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161.
Grace A. Bennett Patricia A. Swift George B. Mullen Jeffrey T. Mitchell Stanley D. Allen Wendy E. Jones C. Richard Kinsolving Vassil St. Georgiev 《Helvetica chimica acta》1988,71(7):1622-1629
The synthesis and antifungal activity of a novel series of 1-[(3,5-bisaryl-2-methylisoxazolidin-3-yl)methyl]-1H-1,2,4-triazoles 6 and 7 (i.e. 8 – 19 ) are discussed. The preparation of 8 – 19 was straightforward and highlighted by a regiospecific 1,3-dipolar cycloaddition of α-substituted (E)-ketonitrones 4 with appropriate atyrene derivatives 5 that led to a cis/trans-diastereoisomeric mixture of the corresponding triazoles (Scheme). The title compounds were evaluated for in vitro antifungal activity in solid agar cultures against a broad array of yeast and systemic mycoses and dermatophytes. The in vivo activity was determined in an immune-compromised mouse model of systemic candidiasis. While the in vitro activity was evident throughout the series, it was moderate in potency. However, some of the triazole derivatives demonstrated a potent in vivo activity comparable to that of the standard drug ketoconazole. Analogue 12 (PR 988-399) emerged as the best overall compound demonstrating potent antifungal activity in both in vitro and in vivo assays. 相似文献
162.
Chemical or electrochemical reduction of the 1,4,7-trithiacyclononane (9S3) complexes [MII(9S3)2][BF4]2 (M = Re (3a) or Tc (3b)) results in instantaneous C-S bond cleavage to yield ethene and the stable MIII thiolate complexes [MIII(9S3)L][BF4] (M = Re (4a) or Tc (4b), L = SCH2CH2SCH2CH2S). Compounds 4 have been characterized by 1H NMR spectroscopy, and the pseudo-octahedral geometry of 4b has been confirmed by X-ray crystallography. Upon electrochemical reduction 4a loses ethene, while 4b can be reversibly reduced to [TcII(9S3)L], which is then further reduced to Tc(I) with loss of ethene. Successive ethene loss is observed in the mass spectra of compounds 3 and 4. The radiosynthesis of 4a with 188Re can be comfortably completed within 10 min starting with 188ReO4- from a 188W/188Re generator, with a radiochemical yield in excess of 90%, and thus represents a practical approach to the preparation of stable 188Re (and 99mTc) thioether complex derivatives/conjugates for clinical use. Crystal data: 4b, C10H20S6Tc, orthorhombic Pbca, a = 12.233(2) A, b = 14.341(2) A, c = 20.726(3) A, Z = 8. 相似文献
163.
164.
J. Torres J.M. Palomares M.A. Gigosos A. Gamero A. Sola J.J.A.M. van der Mullen 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
An experimental study on the asymmetry of the Balmer Hβ profile in plasmas produced by microwaves at atmospheric pressure is presented. The study is based on the definition of several functions that quantify the asymmetry aspects of the profile. Apart from the asymmetry aspects of the flanks also form-functions are defined that characterize the central part of the profile, the so-called dip or central valley, the combination of the two peaks and the dip in between them. The study shows the experimental dependence of these characteristics on the electron density and control parameters such as the gas flow and the hydrogen admixture ratio. The possible use of these newly introduced profile characteristics to plasma diagnosis is discussed. 相似文献
165.
Thomas J. Mullen Charan Srinivasan Mitchell J. Shuster Mark W. Horn Anne M. Andrews Paul S. Weiss 《Journal of nanoparticle research》2008,10(8):1231-1240
In this perspective, we explore hybrid approaches to nanometer-scale patterning, where the precision of molecular self-assembly
is combined with the sophistication and fidelity of lithography. Two areas––improving existing lithographic techniques through
self-assembly and fabricating chemically patterned surfaces––will be discussed in terms of their advantages, limitations,
applications, and future outlook. The creation of such chemical patterns enables new capabilities, including the assembly
of biospecific surfaces to be recognized by, and to capture analytes from, complex mixtures. Finally, we speculate on the
potential impact and upcoming challenges of these hybrid strategies. 相似文献
166.
Nonlinear least squares optimization problems in which the parameters can be partitioned into two sets such that optimal estimates
of parameters in one set are easy to solve for given fixed values of the parameters in the other set are common in practice.
Particularly ubiquitous are data fitting problems in which the model function is a linear combination of nonlinear functions,
which may be addressed with the variable projection algorithm due to Golub and Pereyra. In this paper we review variable projection,
with special emphasis on its application to matrix data. The generalization of the algorithm to separable problems in which
the linear coefficients of the nonlinear functions are subject to constraints is also discussed. Variable projection has been
instrumental for model-based data analysis in multi-way spectroscopy, time-resolved microscopy and gas or liquid chromatography
mass spectrometry, and we give an overview of applications in these domains, illustrated by brief case studies. 相似文献
167.
We analyze the transport properties of bilayer quantum Hall systems at total filling factor nu=1 in drag geometries as a function of interlayer bias, in the limit where the disorder is sufficiently strong to unbind meron-antimeron pairs, the charged topological defects of the system. We compute the typical energy barrier for these objects to cross incompressible regions within the disordered system using a Hartree-Fock approach, and show how this leads to multiple activation energies when the system is biased. We then demonstrate using a bosonic Chern-Simons theory that in drag geometries current in a single layer directly leads to forces on only two of the four types of merons, inducing dissipation only in the drive layer. Dissipation in the drag layer results from interactions among the merons, resulting in very different temperature dependences for the drag and drive layers, in qualitative agreement with experiment. 相似文献
168.
All-trans 1,3,4,5-tetrasubstituted γ-butyrolactams 3 and 7 are readily available in one-pot from allyl tetronates or 4-allyloxycoumarins and amines via a four-step domino Claisen-Conia ring-opening transamidation reaction. 相似文献
169.
An experimental study of the population densities of excited states confirms the existence of the complete excitation saturation phase in the argon neutral system. Collisional radiative coefficients r(1)m are independent of ne and decrease with decreasing ionization energy. At higher ne-values the levels are observed to come consecutively into Saha equilibrium (PLTE). 相似文献
170.
E. A. H. Timmermans I. A. J. Thomas J. Jonkers E. Hartgers J. A. M. van der Mullen D. C. Schram 《Analytical and bioanalytical chemistry》1998,362(5):440-446
The effect of introducing molecular compounds into argon plasmas has been studied using an expanding microwave induced plasma
at atmospheric pressure. Besides the use of optical emission spectroscopy (OES), also the time dependent behavior of line
intensities during power interruptions has been studied. From the measurements it is found that even an injection of small
amounts of molecular compounds (> 0.5%) leads to important changes in excitation mechanisms in the plasma. It is also found
that in the recombination zone downstream in the plasma an excitation mechanism which is independent of the electron density,
e.g. excitation transfer from metastables or Penning ionization, must be responsible for the excitation of analytes.
Received: 12 February 1998 / Revised: 14 April 1998 / Accepted: 17 April 1998 相似文献