The influence of the O–O isotope substitution on spin dynamics of (La0.25Pr0.75)0.7Ca0.3MnO3: La NMR data

The ¹³⁹La NMR spectra and spin–spin relaxation times have been measured for the ¹⁶O and ¹⁸O isotope-substituted manganite (La_0.25Pr_0.75)_0.7Ca_0.3MnO₃ in the external magnetic field of 5 T. The NMR signal wipe-out has been observed in the ¹⁸O-enriched sample in the charge-ordered state. This phenomenon is connected with a sharp increase in the spin–spin relaxation rate. The great isotope-effect observed provides a clear evidence of an essential role of oxygen motion in controlling the long-range magnetic order in manganites.     

Quantitative MR imaging of targeted SPIO particles on the cell surface and comparison to flow cytometry

Purpose

To detect anti-CEACAM5 targeted superparamagnetic iron oxide (SPIO) particles in vitro on the cell surface by quantitative magnetic resonance (MR) imaging and to compare with flow cytometry.

Materials and Methods

The monoclonal mouse antibody T84.1 and an appropriate IgG isotype antibody were conjugated to dextran-coated SPIO particles. HT29 cells expressing carcinoembryonic antigen (CEACAM5) were treated with antibody-conjugated SPIO particles. Purified cell samples were examined on a 3.0-T MR scanner using a multi-echo spin-echo sequence for MR relaxometry. Aliquots of the cell samples were further treated with a fluorescein isothiocyanate (FITC) anti-dextran antibody and an Alexa Fluor 488 anti-mouse antibody for the corresponding flow cytometry.

Results

MR relaxometry revealed a dose-dependent binding of T84.1-conjugated SPIO particles with a positive correlation between R₂ relaxation rate of cell samples and SPIO particle concentration during incubation (r=0.993, P<.01). Positive correlations were also observed between R₂ relaxation rate and flow cytometry (geometric mean) with both fluorescent antibodies (r=0.972 and r=0.953, both P<.01), respectively.

Conclusion

The study revealed the feasibility of quantitative MR imaging of targeted SPIO particles on the cell surface comparable to flow cytometry.     

Spin excitations in fluctuating stripe phases of doped cuprate superconductors

Using a phenomenological lattice model of coupled spin and charge modes, we determine the spin susceptibility in the presence of fluctuating stripe charge order. We assume the charge fluctuations to be slow compared to those of the spins, and combine Monte Carlo simulations for the charge order parameter with exact diagonalization of the spin sector. Our calculations unify the spin dynamics of both static and fluctuating stripe phases and support the notion of a universal spin excitation spectrum in doped cuprate superconductors.     

Changes in the magnetic structure of (La0.25Pr0.75)0.7Ca0.3MnO3 upon the isotopic substitution of 18O for 16O

A giant isotope effect, wherein the low-temperature metallic state is replaced by an insulator state, was recently observed when ¹⁸O was substituted for ¹⁶O in (La_0.25Pr_0.75)_0.7Ca_0.3MnO₃ [N. A. Babushkina, L. M. Belova, O. Yu. Gorbenko et al., Nature (London) 391, 159 (1998)]. In the present work, the temperature evolution of the magnetic structure of two samples of this compound is studied by neutron diffraction. One sample contained a natural mixture of oxygen isotopes, 99.7% ¹⁶O, while the other was enriched to 75% with the isotope ¹⁸O. It is established that the samples are crystallographically identical at room temperature. As the temperature decreases, the sample with ¹⁶O undergoes successive antiferromagnetic (T _AFM=5150 K) and ferromagnetic (T _FM=110 K) transitions, which lead to the establishment of a noncollinear ferromagnetic structure, while a purely antiferromagnetic (T _AFM=150 K) order arises in the sample with ¹⁸O. The temperature dependences of the intensities of the diffraction peaks associated with the charge ordering differ substantially in samples with ¹⁶O and ¹⁸O, and they correlate with the behavior of their electric resistance and magnetic structure. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 46–51 (10 January 1999)     

Kinetic and mechanistic study on the thermal reactivity of stabilized phosphorus ylides,part 3: [(Acetyl)(arylcarbamoyl)methylene]triphenylphosphoranes and [(alkoxycarbonyl)(arylcarbamoyl)methylene]triphenylphosphoranes and their thiocarbamoyl analogues

A series of five [(acetyl)(arylcarbabmoyl)methylene]triphenyl‐phosphoranes 1a–e and their thiocarbamoyl analogues 2a–e , [(alkoxycarbonyl)(arylcarbamoyl)methylene]triphenylphosphoranes 3a–e and their thiocarbamoyl analogues 4a–e were prepared and fully characterized. All ylides are found under conditions of flash vacuum pyrolysis to fragment giving arylisocyanate or isothiocyanate and acetyl ylides or alkoxy ylides which undergo thermal extrusion of Ph₃PO. A kinetic study shows that these reactions are unimolecular and are of first‐order nature with no significant substituent effect. The thiocarbamoyl ylides 2 react from 4.6 to 42 times faster than their carbamoyl ylides 1 , while the thiocarbamoyl ylides 4 react from 6.6 to 20.9 times faster than their carbamoyl ylides 3 . © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 6–16, 2007     

Affinity chromatography on a hydrophobic matrix using a heterobifunctional ligand

Affinity adsorption chromatographic purification using heterobifunctional ligands and a hydrophobic support is described. Soybean trypsin inhibitor was modified with a detergent, with the result that hydrophobic residues were attached to the inhibitor. On passage through an octyl-Sepharose column the inhibitor was bound to the support. The modified inhibitor was still able to bind trypsin either in free solution or after the inhibitor was bound by the support. This procedure forms the basis for a robust affinity purification technique that can be made very general.     

Target asymmetry measurement of deuteron photodisintegration at a photon energy of 550 MeV

The target asymmetry of the deuteron photodisintegration was measured at a photon energy of 550±50 MeV and at proton center-off-mass angles between 25 and 155 degrees.D-butanol andND ₃ were used as target material yielding a maximum deuteron polarization of 41%. Proton and neutron were detected in coincidence. The data show a structure which cannot be described by the existing analyses.     

Standardization of Crude Extract of Neem Seed Kernels (Azadirachta indica A. Juss) and Commercial Neem Based Formulations Using HPTLC and Extended Length Packed-Columns SFC Method

Two chromatographic techniques are described for the separation and quantitative determination of azadirachtin A and B, salannin, and nimbin present in the crude extract of neem seed kernels and commercial neem based formulations. The high performance thin-layer chromatography (HPTLC) separation of markers was carried out on Merck TLC aluminium sheets of silica gel 60 F254 using ethylacetate-benzene (7.0: 3.0, v/v) as mobile phase. The other technique was based on extended length packed column supercritical fluid chromatographic (PC-SFC) separation of the markers using Cyano column (250 mm × 4.6 mm I.D, S-5.0 μ) and Kromasil 100 NH₂ column (250 mm × 4.6 mm I.D, 5.0 μ) connected in series. The detection was carried out using photodiode array detector at 338 K using methanol-modified carbon dioxide (10%) as the mobile phase at flow rate of 2.0 mL min⁻¹. The current study assesses the effect of extending column length during PC-SFC experiment to obtain maximum resolution between a number of unknown components and known markers present in neem seed extracts. Both the chromatographic methods were validated in terms of precision, robustness, recovery, limits of detection and quantitation. The analysis of variance (ANOVA) and Student’s t-test were applied to correlate the results of quantitative determination of markers by means of HPTLC and PC-SFC method.     

Stability-Indicating High-Performance Thin-Layer Chromatographic Determination of Zidovudine as the Bulk drug and in Pharmaceutical Dosage Forms

JPC – Journal of Planar Chromatography – Modern TLC - A sensitive, selective, precise, and stability-indicating high-performance thin-layer chromatographic method has been established...