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排序方式: 共有289条查询结果,搜索用时 31 毫秒
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W. Muchlinsky E. Rother G. Jander O. Pfundt E. Göte W. Schramek L. W. Janssen J. A. C. Teegan A. Schleicher W. Lüdicke E. Denina J. M. Preston N. Rae J. K. Rummel K. Schierjott J. M. Kolthoff T. Kameda L. Blumen J. Pucherna Fr. Hein H. Pauling 《Analytical and bioanalytical chemistry》1932,89(3-4):128-135
44.
We have reinvestigated the crystal structure and thermal properties of NaMgAl(oxalate)(3).9H(2)O. In the thermal gravimetric analysis the steps of dehydration and decomposition/oxidation yield a mass change that is commensurate with 9 water molecules of hydration. Dehydration steps occur at 127, 171, and 201 degrees C whereas the oxalate ligand decomposes in steps at 403 and 424 degrees C with a final oxidation step at 692 degrees C. A refinement of the single crystal X-ray diffraction data taken at 200 K affirms the P3c1 space group with nine water molecules of hydration and unit cell parameters a = b = 16.7349(2) A and c = 12.6338(1) A with Z = 6. The structures can be described in terms of modulations of an idealised Z = 1 structure in P3[combining macron]lm. T-Cycle experiments of spectral holes in the R(1)-line yield a single Gaussian barrier with T(0) +/- sigma(T) of 46 +/- 21 K and three barriers with 40 +/- 12, 70 +/- 10, 107 +/- 5 K for perprotonated and partially deuterated (46%) NaMgAl(oxalate)(3).9H(2)O/Cr(iii) 0.5%, respectively. 相似文献
45.
Madhab Prasad Bajgai Santosh Aryal Douk Rae Lee Soo-Jin Park Hak Yong Kim 《Colloid and polymer science》2008,286(5):517-524
Amphiphilic graft copolymer composed of poly(∈-caprolactone) and dextran was synthesized by ring opening polymerization of
∈-caprolactone initiated through the hydroxyl end of dextran in the presence of stannous 2-ethylhexanoate [Sn (oct)2] as a catalyst. It has been widely characterized by Fourier transform infrared spectroscopy, 1H NMR, and thermogravimetric analysis. Nanoparticles were prepared in aqueous medium by co-solvent evaporation technique at
room temperature (25 °C). Hydrodynamic diameter and particle size were measured by dynamic light scattering spectroscopy and
atomic force microscopy, respectively. Core-shell geometry of polymeric nanoparticle was characterized by fluorescence spectrophotometer
using pyrene as a probe. Critical micelle concentration of polymer in triple distilled water decreased from 6.9 × 10−4 to 8.9 × 10−4 g/l with increasing hydrophobic moiety. Further, the physiological stability of the nanoparticles in phosphate buffer saline
of pH 7.4 at 37 °C was evaluated, which showed promising in drug delivery system. 相似文献
46.
Kim HM Kim BR An MJ Hong JH Lee KJ Cho BR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(7):2075-2083
2-Acetyl-6-(dimethylamino)naphthalene-derived two-photon fluorescent Ca2+ probes (ACa1-ACa3) are reported. They can be excited by a 780 nm laser beam, show 23-50-fold enhancement in one- and two-photon excited fluorescence in response to Ca2+, emit fourfold stronger two-photon excited fluorescence than Oregon Green 488 BAPTA-1 upon complexation with Ca2+, and can selectively detect intracellular free Ca2+ ions in live cells and living tissues with minimum interference from other metal ions and membrane-bound probes. Moreover, these probes are capable of monitoring calcium waves at a depth of 120-170 microm in live tissues for 1100-4000 s using two-photon microscopy with no artifacts of photobleaching. 相似文献
47.
Kim HM Jeong BH Hyon JY An MJ Seo MS Hong JH Lee KJ Kim CH Joo T Hong SC Cho BR 《Journal of the American Chemical Society》2008,130(13):4246-4247
We report a new two-photon fluorescence turn-on probe 6-[(E)-3-oxo-1-dodecenyl]-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (CL2) that is designed specifically for visualizing lipid rafts in living cells and tissues. This probe emits much brighter two-photon excited fluorescence in lipid rafts than in non-raft domains and allows direct visualization of the lipid rafts in the live cells and pyramidal neuron layer of the CA1 region at a depth of 100-250 mum in live tissues using two-photon microscopy. 相似文献
48.
Enantioselective Generation of Adjacent Stereocenters in a Copper‐Catalyzed Three‐Component Coupling of Imines,Allenes, and Diboranes 下载免费PDF全文
Kay Yeung Rebecca E. Ruscoe Dr. James Rae Dr. Alexander P. Pulis Prof. Dr. David J. Procter 《Angewandte Chemie (International ed. in English)》2016,55(39):11912-11916
A highly enantio‐ and diastereoselective copper‐catalyzed three‐component coupling affords the first general synthesis of homoallylic amines bearing adjacent stereocenters from achiral starting materials. The method utilizes a commercially available NHC ligand and copper source, operates at ambient temperature, couples readily available simple imines, allenes, and diboranes, and yields high‐value homoallylic amines that exhibit versatile amino, alkenyl, and boryl units. 相似文献
49.
Kim HM Yang PR Seo MS Yi JS Hong JH Jeon SJ Ko YG Lee KJ Cho BR 《The Journal of organic chemistry》2007,72(6):2088-2096
A novel, two-photon probe for the detection of free Mg2+ ions in living cells and live tissues has been developed. The probe can be excited by 880 nm laser photons, emits strong two-photon excited fluorescence in response to Mg2+ ions, can be easily loaded into the cell and tissue, shows high photostability, and can measure the Mg2+ ion concentration without interference by Ca2+ ions in living cells. The intracellular dissociation constant (Kdi) for Mg2+ determined by the two-photon process is 2.5 mM, which is suitable for dynamic Mg2+ concentration measurement. In addition, the probe is capable of imaging endogenous stores of free Mg2+ at a few hundred micrometers depth in live tissues using two-photon microscopy (TPM). 相似文献
50.
Soo‐Jin Park Min‐Kang Seo Jae‐Rock Lee Douk‐Rae Lee 《Journal of polymer science. Part A, Polymer chemistry》2001,39(1):187-195
To investigate the effect of catalysts on the thermal, rheological, and mechanical properties of an epoxy system, a resin based on diglycidyl ether of bisphenol‐A (DGEBA) was cured by two cationic latent thermal catalysts, N‐benzylpyrazinium hexafluoroantimonate (BPH) and N‐benzylquinoxalinium hexafluoroantimonate (BQH). Differential scanning calorimetry was used for the thermal characterization of the epoxy systems. Near‐infrared spectroscopy was employed to examine the cure reaction between the DGEBA and the latent thermal catalysts used. The rheological properties of the blend systems were investigated under an isothermal condition with a rheometer. To characterize the mechanical properties of the systems, flexure, fracture toughness (KIC), and impact tests were performed. The phase morphology was studied with scanning electron microscopy of the fractured surfaces of mechanical test samples. The conversion and cure activation energy of the DGEBA/BQH system were higher than those of the DGEBA/BPH system. The crosslinking activation energy showed a result similar to that obtained from the cure kinetics of the blend systems. The flexure strength, KIC, and impact properties of the DGEBA/BQH system were also superior to those of the DGEBA/BPH system. This was a result of the substituted benzene group of the BQH catalyst, which increased the crosslink density and structural stability of the epoxy system studied. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 187–195, 2001 相似文献