Decomposition of the Unsteady Wave Patterns for Bessho form Translating-Pulsating Source Green Function

In order to interpret the physical feature of Bessho form translating-pulsating source Green function, the phase function is extracted from the integral representation and stationary-phase analysis is carried out in this paper. The complex characteristics of the integral variable and segmentation of the integral intervals are discussed in m complex plane. In θ space, the interval [-π/2+φ,-π/2+φ-iε] is dominant in the near-field flow, and there is a one-to-one correspondence between the real intervals in m space and the unsteady wave patterns in far field. If 4τ>1(τ is the Brard number), there are three kinds of propagation wave patterns such as ring-fan wave pattern, fan wave pattern and inner V wave pattern, and if 0<4τ<1, a ring wave pattern, an outer V and inner V wave pattern are presented in far field. The ring-fan or ring wave pattern corresponds to the interval [-π+α,-π/2+φ] for integral terms about k2, and the fan or outer V wave pattern and inner V wave pattern correspond to [-π+α,-π/2) and(-π/2,-π/2+φ] respectively for terms about k1. Numerical result shows that it is beneficial to decompose the unsteady wave patterns under the condition of τ≠0 by converting the integral variable θ to m. In addition, the constant-phase curve equations are derived when the source is performing only pulsating or translating.

Identification of Persister Drug Combination Clinafloxacin+Cefuroxime+Gentamicin That Eradicates Persistent Pseudomonas aeruginosa Infection in a Murine Cystic Fibrosis Model

Pseudomonas aeruginosa can cause persistent infections,such as biofilm infections,in cystic fibrosis patients,which are difficult to cure due to non-growing persister bacteria that are not effectively killed by the current treatments.While antibiotic activity against growing P.aeruginosa is well documented,their activity against non-growing stationary phase cultures is less clear.Here,we evaluated six major classes of antibiotics,including cell wall and cell membrane inhibitors,protein synthesis inhibitors,DNA synthesis inhibitors,RNA synthesis inhibitors,sulfa drugs and nitrofurantoin,for their activity against growing and non-growing P.aeruginosa.We foundthat cell wall and cell membrane inhibitors(cefuroxime and colistin),DNA synthesis inhibitors(clinafloxacin)and sulfa drugs(sulfamethoxazole)had good activity against stationary-phase bacteria,while protein synthesis inhibitors(gentamicin),RNA synthesis inhibitor(rifampin)and nitrofurantoin showed relatively poor activity.Clinafloxacin was the only drug able to completely eradicate stationary-phase bacteria within four days.The cefuroxime+gentamicin+clinafloxacin combination was able to kill all bacteria from a biofilm within two days,whereas the clinically used drug combination cefuroxime+gentamicin/colistin only partially killed the biofilmbacteria.In amurine persistent cystic fibrosis lung infectionmodel,only the cefuroxime+gentamicin+clinafloxacin drug combination eradicated all bacteria from the lungs,whereas clinafloxacin alone,cefuroxime+clinafloxacin or the currently recommended drug combination cefuroxime+gentamicin failed to do so.The complete eradication is a property of the clinafloxacin combination,as the otherwise identical levofloxacin combination did not clear the bacterial loads from the lungs.Our findings offer new therapeutic options for more effective treatment of persistent P.aeruginosa infections,with possible implications for treating other persistent infections.

SURFACE AND INTERFACIAL GRAVITY WAVES INDUCED BY AN IMPULSIVE DISTURBANCE IN A TWO-LAYER INVISCID FLUID

The transient gravity waves due to an impulsive source in a two-layer fluid system are investigated analytically. The fluid is assumed to be inviscid and incompressible. The density of each of the two layers is constant. Five different boundary conditions are considered. The depth of each of the two layers is infinite or finite. The upper fluid of finite depth is covered by a rigid lid or a free surface. Based on the assumption of small-amplitude waves, a linear system is established. The integral solutions for the free-surface and interfacial waves are obtained by means of the Fourier-Laplace transform. The corresponding asymptotic representations are derived for large time with a fixed distance-to-time ratio by the Stokes and Scorer methods of stationary phase. The analytical solutions show that there are two different modes, namely the free-surface and interracial wave modes. The wave profiles observed depend on the relation between the distance-to-time ratio and the maximal group velocities and on the limiting values of the second derivatives of the frequencies as well.