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101.
Manning DA Lopez-Capel E White ML Barker S 《Rapid communications in mass spectrometry : RCM》2008,22(8):1187-1195
A gas-tight thermal analysis system (Netzsch STA 449C Jupiter) has been connected to an isotope ratio mass spectrometer (PDZ Europa 20-20) via an interface containing an oxidizing furnace, water trap, and gas-sampling valve. Using this system, delta(13)C has been measured for CO(2) derived from the thermal decomposition of carbonate and oxalate minerals and organic materials at temperatures that correspond to different decomposition events. There is close agreement between measured and published delta(13)C values for carbonate and oxalate minerals, which have simple decarbonation reactions on heating. Cellulose and lignin-rich materials show much more complex thermal decomposition, reflecting differences in their purity and structure, and measured delta(13)C values vary with the temperature of gas sampling. Provided that measurements are made at temperatures that correspond to the decomposition of cellulose and lignin (indicated by maximum weight loss), internally consistent data can be obtained. However, measurements for cellulose and lignin are systematically enriched in delta(13)C (by up to 1.4 per thousand) with respect to those reported for reference materials, possibly due to the slower combustion kinetics (compared with EA-IRMS). Thermogravimetric analysis/isotope ratio mass spectrometry (TG-IRMS) is ideal for materials and samples for which it is not possible to use other isotopic measurement techniques, for example because of sample heterogeneity. 相似文献
102.
Francis E. Appoh Marcy J. Manning Teri J. Gullon Margaret A. Hansen Emily C. Bevans Krista D. M. Hogan Courtney S. Turner Christopher M. Vogels Andreas Decken Stephen A. Westcott 《Central European Journal of Chemistry》2008,6(3):359-364
The Ugi reaction with formylphenylboronic acid derivatives as the carbonyl component proceeds to give the corresponding boron-containing
dipeptide derivatives (Ugi products) in good yields.
相似文献
103.
Manning TJ Thomas J Osiro S Smith J Abadi G Noble L Phillips D 《Natural product research》2008,22(5):399-413
In this computational study, geometric factors are calculated by applying semi-empirical methods (PM3) that support experimental evidence from this lab where bryostatins can bind trivalent iron with six Fe-O bonds forming an octahedral geometry. The geometric factors are calculated for all 20 structures (Fe3+ bound to bryostatin 1-20) as a neutral, monovalent, and divalent species. The average Fe-O bond distances and bond angles are compared to those of known marine and terrestrial siderophores. From these two data sets, we then examined other known marine natural products (MNPs) that can form a hexavalent complex with six Fe-O bonds and draw conclusions about their potential biological role as marine siderophores. This computational data indicates that Fe(III) strongly bonds to a host of MNPs, increasing their water solubility, contracting their structure, hence allowing transport through cell membranes more readily, and in some cases, stabilizing ester bonds that are susceptible to hydrolysis. It is argued that administering medicinally bryostatin, its analogs or other MNPs as a ferric complex, holds some fundamental chemical advantages compared to its administration as a neutral uncomplexed species. 相似文献
104.
Pyrenophane (6) and an octaphenyl derivative (16) were synthesized using two different routes. Both cyclophanes contain a severely bent pyrene unit (6: theta = 93.6 degrees and 16: theta = 95.8 degrees , according to DFT-calculations (B3LYP/6-311G**)), which was generated at room temperature by a valence isomerization/dehydrogenation (VID) reaction. HOMA and NICS indicate 92-98% retention of aromaticity of the highly distorted pyrene systems compared to planar pyrene. 相似文献
105.
Francis A. Appoh Stephanie S. Barnes Marcy J. Manning Courtney S. Turner Christopher M. Vogels Stephen A. Westcott Andreas Decken 《Journal of heterocyclic chemistry》2008,45(5):1415-1418
106.
Montague M Ducker RE Chong KS Manning RJ Rutten FJ Davies MC Leggett GJ 《Langmuir : the ACS journal of surfaces and colloids》2007,23(13):7328-7337
The UV photo-oxidation of oligo(ethylene glycol) (OEG)-terminated self-assembled monolayers (SAMs) has been studied using static secondary ion mass spectrometry, X-ray photoelectron spectroscopy, contact angle measurement, and friction force microscopy. OEG-terminated SAMs are oxidized to yield sulfonates, but photodegradation of the OEG chain also occurs on a more rapid time scale, yielding degradation products that remain bound to the surface via gold-sulfur bonds. The oxidation of these degradation products is the rate-limiting step in the process. Photopatterning of OEG-terminated SAMs may be accomplished by using a mask and suitable light source or by using scanning near-field photolithography (SNP) in which the mask is replaced by a scanning near-field optical microscope coupled to a UV laser. Using SNP, it is possible to fabricate patterns in SAMs with a full width at half-maximum height (fwhm) as small as 9 nm, which is approximately 15 times smaller than the conventional diffraction limit. SNP-patterned OEG-terminated SAMs may be used to fabricate protein nanopatterns. By adsorbing carboxylic acid-terminated thiols into oxidized regions and converting these to active ester intermediates, it has been possible to fabricate lines of protein molecules with widths of only a few tens of nanometers. 相似文献
107.
Owen DM Auksorius E Manning HB Talbot CB de Beule PA Dunsby C Neil MA French PM 《Optics letters》2007,32(23):3408-3410
We present a time-gated, optically sectioned, hyperspectral fluorescence lifetime imaging (FLIM) microscope incorporating a tunable supercontinuum excitation source extending into the UV. The system is capable of resolving the excitation spectrum, emission spectrum, and fluorescence decays in an optically sectioned image. 相似文献
108.
Salmanca Oviedo LN Gomez-Herrero A Landa Canovas AR Otero-Diaz LC 《Micron (Oxford, England : 1993)》2000,31(5):597-603
Two new misfit layer structures have been synthesized within the Sb-Nb-Se system. Powder X-ray diffraction and electron microscopy techniques (electron diffraction, HREM, XEDS) have been used to determine the nature of their structure. According to TEM and XEDS data (for more than 15 crystals studied) both phases are monolayer type, i.e. (SbSe)1+delta (NbSe2). Electron microscopy reveals a composite modulated structure that consists of the periodical intergrowth of a pseudotetragonal SbSe layer, denominated as Q, and a pseudohexagonal layer NbSe2, denominated as H. Both layers fit along b, stack along c and do not fit along a (misfit) giving rise to an incommensurate modulation along this direction. The two phases differ in the symmetry of the Q layers being in one case orthorhombic (for delta = 0.17) and monoclinic in the other (for delta = 0.19). After the characterization of the sample by electron microscopy the unit cells of the basic layers could be refined for both phases by powder X-ray diffraction: aQ = 5.824(2) A, bQ = 5.962(5) A, cQ = 23.927(6) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees and aH = 3.415(5) A, bH = 5.962(6) A,, cH = 11.962(1) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees for the orthorhombic phase; aQ = 5.844(2) A, bQ = 5.981(1) A, cQ = 23.919(5) A, alpha = 90 degrees, beta = 90 degrees and gamma = 96.00(3)degrees and aH = 3.439(1) A, bH = 5.994(2) A, cH = 11.956(3) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees for the monoclinic phase. The phase with the monoclinic Q-sublattice often appears as twinned crystals. The more abundant crystals are disordered intergrowths of both monolayer phases. 相似文献
109.
Magnetic resonance in the era of molecular imaging of cancer 总被引:1,自引:0,他引:1
Gore JC Manning HC Quarles CC Waddell KW Yankeelov TE 《Magnetic resonance imaging》2011,29(5):587-600
Magnetic resonance imaging (MRI) has played an important role in the diagnosis and management of cancer since it was first developed, but other modalities also continue to advance and provide complementary information on the status of tumors. In the future, there will be a major continuing role for noninvasive imaging in order to obtain information on the location and extent of cancer, as well as assessments of tissue characteristics that can monitor and predict treatment response and guide patient management. Developments are currently being undertaken that aim to provide improved imaging methods for the detection and evaluation of tumors, for identifying important characteristics of tumors such as the expression levels of cell surface receptors that may dictate what types of therapy will be effective and for evaluating their response to treatments. Molecular imaging techniques based mainly on radionuclide imaging can depict numerous, specific, cellular and molecular markers of disease and have unique potential to address important clinical and research challenges. In this review, we consider what continuing and evolving roles will be played by MRI in this era of molecular imaging. We discuss some of the challenges for MRI of detecting imaging agents that report on molecular events, but highlight also the ability of MRI to assess other features such as cell density, blood flow and metabolism which are not specific hallmarks of cancer but which reflect molecular changes. We discuss the future role of MRI in cancer and describe the use of selected quantitative imaging techniques for characterizing tumors that can be translated to clinical applications, particularly in the context of evaluating novel treatments. 相似文献
110.
Robert S. Manning 《Journal of Elasticity》2014,115(2):105-130
We catalogue configurations that locally minimize energy for a planar elastic rod (extensible-shearable or inextensible-unshearable) subject to arbitrary Dirichlet boundary conditions in position and orientation. Via a combination of analysis and computation, we determine several bifurcation surfaces in the 3-parameter space of boundary conditions and explore how they depend on the rod material parameters, including in the inextensible limit. For each possible boundary condition, we find all stable equilibria with sufficiently low energy that they might be competitive within a Boltzmann distribution if the rod were used to model DNA with tens or hundreds of base pairs, the length-scale relevant for DNA looping. Depending on the boundary conditions, there are as many as three such equilibria. 相似文献