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1.
This paper is concerned with the implementation and testing of an algorithm for solving constrained least-squares problems. The algorithm is an adaptation to the least-squares case of sequential quadratic programming (SQP) trust-region methods for solving general constrained optimization problems. At each iteration, our local quadratic subproblem includes the use of the Gauss–Newton approximation but also encompasses a structured secant approximation along with tests of when to use this approximation. This method has been tested on a selection of standard problems. The results indicate that, for least-squares problems, the approach taken here is a viable alternative to standard general optimization methods such as the Byrd–Omojokun trust-region method and the Powell damped BFGS line search method. 相似文献
2.
Thorsten Hamann Erin Osborne Heather L. Youngs Julie Misson Laurent Nussaume Chris Somerville 《Cellulose (London, England)》2004,11(3-4):279-286
We have used Affymetrix gene chips to measure the expression of 10 CESA and 29 CSL genes of Arabidopsis in different developmental stages or organs. These measurements reveal that many of the genes exhibit different levels of expression in the various organs. While several CESA genes are highly expressed in all the tissues examined, very few CSL genes approach such high levels of expression. This suggests that the CSL genes either encode enzymes for the synthesis of minor components of cell walls or are expressed only in specific cell types. The expression data also highlights the potential importance of the CESA genes for primary and secondary cell wall formation during different developmental stages and in the different organs examined. 相似文献
3.
Given one or more vibrational modes of a membrane, the free vibration equation can be applied to infer the mass surface density. This paper considers determining the surface density of an inhomogeneous membrane from digitized holographic projections (interferograms) of the modeshapes. Spatially discrete numerical models of the membrane surface are presented, which can be used to solve both forward and inverse vibration problems. The accuracy of the discrete models is examined for exactly solvable free vibration problems involving inhomogeneous membranes. For the solution of the inverse problem, error estimates are given for the mass surface density deduced from modeshape interferograms. The practicability of the method is investigated using simulated experimental data for membranes with composite and continuously inhomogeneous density profiles. Strategies are discussed for reducing errors in the reconstructed densities. 相似文献
4.
The effect of variation of the scattered light intensity in a magnetic fluid with aggregates of magnetite particles several microns in size under the action of a magnetic field is studied. The effect relaxation times are determined when the magnetic field is turned on and off. This effect is found to be caused by the orientation of anisotropically magnetized aggregates. Experimental data are used to calculate the average anisotropy of the magnetic susceptibility of the aggregate and estimate its magnetic permeability. 相似文献
5.
6.
K. V. Erin 《Colloid Journal》2007,69(6):700-705
The effects of alternating and pulsed fields on the electric birefringence in a colloided system of magnetite particles suspended in kerosene are studied. The permanent dipole moment is found to substantially influence the orientation of magnetite particles in alternating fields with frequencies of higher than 15 Hz. The mechanism for the generation of the permanent dipole moments in magnetite colloidal particles suspended in low-conductivity liquids is discussed. 相似文献
7.
The energy profiles for the decomposition of the first triplet of acetaldehyde via the reactions: CH3CHOν → CH3CO° + H°, CH3CHO* → CH.3 + HCO., have been computed using a non-empirical LCAO MO SCF procedure. Both reactions were found to have energy barriers of similar height (245 KJ mole ?1) and at similar extensions of the respective rupturing bonds (0.71–0.76 Å). The energy profile for internal rotation about the C-C bond was also calculated and showed a small barrier (3.5 kJ mole?1). 相似文献
8.
Jo E Sanna MG Gonzalez-Cabrera PJ Thangada S Tigyi G Osborne DA Hla T Parrill AL Rosen H 《Chemistry & biology》2005,12(6):703-715
The essential role of the sphingosine 1-phosphate (S1P) receptor S1P(1) in regulating lymphocyte trafficking was demonstrated with the S1P(1)-selective nanomolar agonist, SEW2871. Despite its lack of charged headgroup, the tetraaromatic compound SEW2871 binds and activates S1P(1) through a combination of hydrophobic and ion-dipole interactions. Both S1P and SEW2871 activated ERK, Akt, and Rac signaling pathways and induced S1P(1) internalization and recycling, unlike FTY720-phosphate, which induces receptor degradation. Agonism with receptor recycling is sufficient for alteration of lymphocyte trafficking by S1P and SEW2871. S1P(1) modeling and mutagenesis studies revealed that residues binding the S1P headgroup are required for kinase activation by both S1P and SEW2871. Therefore, SEW2871 recapitulates the action of S1P in all the signaling pathways examined and overlaps in interactions with key headgroup binding receptor residues, presumably replacing salt-bridge interactions with ion-dipole interactions. 相似文献
9.
Mosley DW Sellmyer MA Daida EJ Jacobson JM 《Journal of the American Chemical Society》2003,125(35):10532-10533
Adlayers were formed on self-assembled monolayers (SAMs) formed by alkanethiols on gold. Base SAMs exposing amide functional groups at the SAM surface were formed with 12-mercaptododecanamide. Adlayers of diacetylene-containing monomers were then formed via amide hydrogen bonding in decalin and decalin/toluene mixtures. Grazing angle FTIR, contact angle measurements, and ellipsometry suggest that these adlayer films exhibit ordering and packing similar to that of SAMs on gold. Resonance Raman spectroscopy showed that these diacetylene adlayers could be readily polymerized by exposure to UV light. 相似文献
10.
A series of chiral aromatic imides and diimides were synthesized and their electrochemical, absorption, fluorescent, and chiroptical properties were examined for their potential application as molecular chiroptical switches. These compounds exhibit strong UV-vis absorptions, and can be electrochemically reduced to radical anions that absorb in the near infrared (NIR) region. Further reduction to the dianionic states results in new absorptions in the visible region. The changes in circular dichroism upon redox switching were apparent in the UV-vis region but were absent in the NIR region. 相似文献