The method of boundary integral equations is developed as applied to initial-boundary value problems for strictly hyperbolic
systems of second-order equations characteristic of anisotropic media dynamics. Based on the theory of distributions (generalized
functions), solutions are constructed in the space of generalized functions followed by passing to integral representations
and classical solutions. Solutions are considered in the class of singular functions with discontinuous derivatives, which
are typical of physical problems describing shock waves. The uniqueness of the solutions to the initial-boundary value problems
is proved under certain smoothness conditions imposed on the boundary functions. The Green’s matrix of the system and new
fundamental matrices based on it are used to derive integral analogues of the Gauss, Kirchhoff, and Green formulas for solutions
and solving singular boundary integral equations. 相似文献
The interactions between channels and their cognate blockers are at the heart of numerous biomedical phenomena. Herein, we unravel one particularly important example bearing direct pharmaceutical relevance: the blockage mechanism of the influenza M2 channel by the anti-flu amino-adamantyls (amantadine and rimantadine) and how the channel and, consequently, the virus develop resistance against them. Using both computational analyses and experimental verification, we find that amino-adamantyls inhibit M2's H(+) channel activity by electrostatic hindrance due to their positively charged amino group. In contrast, the hydrophobic adamantyl moiety on its own does not impact conductivity. Additionally, we were able to uncover how mutations in M2 are capable of retaining drug binding on the one hand yet rendering the protein and the mutated virus resistant to amino-adamantyls on the other hand. We show that the mutated, drug-resistant protein has a larger binding pocket for the drug. Hence, despite binding the channel, the drug remains sufficiently mobile so as not to exert a H(+)-blocking positive electrostatic hindrance. Such insight into the blocking mechanism of amino-adamantyls, and resistance thereof, may aid in the design of next-generation anti-flu agents. 相似文献
Given a graph with n nodes and minimum degree δ, we give a polynomial time algorithm that constructs a partition of the nodes of the graph into two sets X and Y such that the sum of the minimum degrees in X and in Y is at least δ and the cardinalities of X and Y differ by at most δ(δ + 1 if n ≠ δ(mod 2)). The existence of such a partition was shown by Sheehan (1988). 相似文献
The Peyrard-Bishop model, which describes the dynamics of a DNA molecule, is considered. The solutions that represent discrete breathers are derived in the framework of the model. The dynamic stability of the stationary discrete breathers with respect to small perturbations is studied. The solutions can be interpreted as the experimentally observed opening of the base pairs in the DNA double strand at the initial stages of denaturation. It is also demonstrated that the model allows the existence of mobile breathers that move in the absence of perturbations in the environment. The interaction of the mobile breathers is numerically simulated. The Peierls-Nabarro barrier and the effective mass and velocity of the breather are estimated. 相似文献
α-Cyclopiazonic acid (CPA) is a tremorgenic mycotoxin produced by Aspergillus and Penicillium fungal species, commonly found on agricultural commodities or fermented food products. A sensitive and rapid imaging surface plasmon resonance (iSPR) assay was developed to detect CPA in maize and cheese by combining an indirect competitive immunoassay and signal amplification based upon a secondary antibody (Ab2) conjugated with gold nanoparticles. Matrix-matched calibration curves were used to determine CPA content in maize and cheese samples. Recoveries, at two spiking levels in maize and cheese, were 89 to 126%, with standard deviations of repeatability (RSDr) of less than 16%. The limits of detection were 17 and 6 μg/kg in maize and cheese, respectively. To separate the CPA-contaminated samples from uncontaminated samples, a cutoff validation level of 40 μg/kg was introduced. The assay was applied to samples of naturally contaminated maize and was compared with competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA). This is the first report to detect CPA using an immuno-biosensor iSPR format.
A new method for the quantitative extraction and separation of trace amounts of rhodium from nitric acid and sodium trichloroacetate
media has been established based on the formation of an ion-association complex of hexahydrated rhodium cation Rh(H2O)63+ and the trichloroacetate (TCA) anion in tri-n-butyl phosphate (TBP). The effect of various factors (solvent, pH, sodium trichloroacetate,
shaking time, phase volume ratio, composition of the extracted species, foreign ions, transformation of rhodium chlorocomplexes
into hexahydrated cation, etc.) on the extraction and back-extraction of rhodium has been investigated. The method can be
combined with subsequent FAAS determination of rhodium. The procedure was applied to determine rhodium traces in chloroplatinic
acid and palladium chloride.
Received: 17 March 2000 / Revised: 15 May 2000 / Accepted: 19 May 2000 相似文献