Log-periodic modulation in one-dimensional random walks

We have studied the diffusion of a single particle on a one-dimensional lattice. It is shown that, for a self-similar distribution of hopping rates, the time dependence of the mean-square displacement follows an anomalous power law modulated by logarithmic periodic oscillations. The origin of this modulation is traced to the dependence on the length of the diffusion coefficient. Both the random walk exponent and the period of the modulation are analytically calculated and confirmed by Monte Carlo simulations.Comment: 6 pages, 7 figure

Supernova Remnant Kes 17: Efficient Cosmic Ray Accelerator inside a Molecular Cloud

Supernova remnant Kes 17 (SNR G304.6+0.1) is one of a few but growing number of remnants detected across the electromagnetic spectrum. In this paper, we analyze recent radio, X-ray, and gamma-ray observations of this object, determining that efficient cosmic ray acceleration is required to explain its broadband non-thermal spectrum. These observations also suggest that Kes 17 is expanding inside a molecular cloud, though our determination of its age depends on whether thermal conduction or clump evaporation is primarily responsible for its center-filled thermal X-ray morphology. Evidence for efficient cosmic ray acceleration in Kes 17 supports recent theoretical work that the strong magnetic field, turbulence, and clumpy nature of molecular clouds enhances cosmic ray production in supernova remnants. While additional observations are needed to confirm this interpretation, further study of Kes 17 is important for understanding how cosmic rays are accelerated in supernova remnants.Comment: 13 pages, 6 figures, 4 table

An Evaluation of the Additional Acoustic Power Needed to Overcome the Effects of a Test-Articles Absorption During Reverberant Chamber Acoustic Testing of Spaceflight Hardware

It is important to realize that some test-articles may have significant sound absorption that may challenge the acoustic power capabilities of a test facility. Therefore, to mitigate this risk of not being able to meet the customers target spectrum, it is prudent to demonstrate early-on an increased acoustic power capability which compensates for this test-article absorption. This paper describes a concise method to reduce this risk when testing aerospace test-articles which have significant absorption. This method was successfully applied during the SpaceX Falcon 9 Payload Fairing acoustic test program at the NASA Glenn Research Center Plum Brook Stations RATF

An Evaluation of the Additional Acoustic Power Needed to Overcome the Effects of a Test-Article's Absorption during Reverberant Chamber Acoustic Testing of Spaceflight Hardware

The exposure of a customers aerospace test-article to a simulated acoustic launch environment is typically performed in a reverberant acoustic test chamber. The acoustic pre-test runs that will ensure that the sound pressure levels of this environment can indeed be met by a test facility are normally performed without a test-article dynamic simulator of representative acoustic absorption and size. If an acoustic test facilitys available acoustic power capability becomes maximized with the test-article installed during the actual test then the customers environment requirement may become compromised. In order to understand the risk of not achieving the customers in-tolerance spectrum requirement with the test-article installed, an acoustic power margin evaluation as a function of frequency may be performed by the test facility. The method for this evaluation of acoustic power will be discussed in this paper. This method was recently applied at the NASA Glenn Research Center Plum Brook Stations Reverberant Acoustic Test Facility for the SpaceX Falcon 9 Payload Fairing acoustic test program

Master Operators Govern Multifractality in Percolation

Using renormalization group methods we study multifractality in percolation at the instance of noisy random resistor networks. We introduce the concept of master operators. The multifractal moments of the current distribution (which are proportional to the noise cumulants $C_R^{(l)} (x, x^\prime)$ of the resistance between two sites x and $x^\prime$ located on the same cluster) are related to such master operators. The scaling behavior of the multifractal moments is governed exclusively by the master operators, even though a myriad of servant operators is involved in the renormalization procedure. We calculate the family of multifractal exponents ${\psi_l}$ for the scaling behavior of the noise cumulants, $C_R^{(l)} (x, x^\prime) \sim | x - x^\prime |^{\psi_l /\nu}$, where $\nu$ is the correlation length exponent for percolation, to two-loop order.Comment: 6 page

Averaged residence times of stochastic motions in bounded domains

Two years ago, Blanco and Fournier (Blanco S. and Fournier R., Europhys. Lett. 2003) calculated the mean first exit time of a domain of a particle undergoing a randomly reoriented ballistic motion which starts from the boundary. They showed that it is simply related to the ratio of the volume's domain over its surface. This work was extended by Mazzolo (Mazzolo A., Europhys. Lett. 2004) who studied the case of trajectories which start inside the volume. In this letter, we propose an alternative formulation of the problem which allows us to calculate not only the mean exit time, but also the mean residence time inside a sub-domain. The cases of any combinations of reflecting and absorbing boundary conditions are considered. Lastly, we generalize our results for a wide class of stochastic motions.Comment: 7 pages, 3 figure

Cell-wall-inhibiting antibiotic combinations with activity against multidrug-resistant Klebsiella pneumoniae and Escherichia coli

AbstractThe increasing prevalence of hospital and community-acquired infections caused by multidrug-resistant (MDR) bacterial pathogens is rapidly limiting the options for effective antibiotic therapy. Systematic studies on combinations of already available antibiotics that could provide an effective treatment against MDR bacteria are needed. We tested combinations of antibiotics that target one important physiological function (peptidoglycan synthesis) at several steps, and studied Enterobacteriaceae (Klebsiella pneumoniae and Escherichia coli) for which multidrug resistance associated with ESBL-producing plasmids has become a major problem. To measure the effectiveness of antibiotics alone and in combination, we used checkerboard assays, static antibiotic concentration time-kill assays, and an improved in-vitro kinetic model that simulates human pharmacokinetics of multiple simultaneously administered antibiotics. The target strains included an MDR K. pneumoniae isolate responsible for a recent major hospital outbreak. A double combination (fosfomycin and aztreonam) and a triple combination (fosfomycin, aztreonam and mecillinam) were both highly effective in reducing bacterial populations in all assays, including the in vitro kinetic model. These combinations were effective even though each of the MDR strains was resistant to aztreonam alone. Our results provide an initial validation of the potential usefulness of a combination of antibiotics targeting peptidoglycan synthesis in the treatment of MDR Gram-negative bacteria. We suggest that a combination of fosfomycin with aztreonam could become a useful treatment option for such infections and should be further studied

Production of Polyclonal Antibodies Against a Yam Isolate of Cucumber Mosaic Virus (Cmv).

Cucumber mosaic virus (CMV) genus Cucumovirus was recently detected in yam in Ghana, Togo and Benin bringing to six the total number of countries reporting CMV infection in yam worldwide. Two serotypes of CMV are distinguished and a specific antibody against the yam isolate of CMV is currently not available. Rabbit polyclonal antibodies were produced against purified preparations of a yam isolate of CMV from Nigeria. The antibody titre was determined by Protein-A sandwich (PAS) enzymelinked immunosorbent assay (ELISA) and antigen-coated plate (ACP) ELISA. Antigen detection limit of the antibody was determined by PAS-ELISA using serial dilutions of infected sap. The CMV antiserum produced had a titre of 1:25,600 and 1:64,000 by PAS- and ACP-ELISA, respectively and a sap dilution end point of 1:160. The antibody detected homologous antigen in infected yam leaves from Ghana, Togo, Benin and Nigeria. The CMV polyclonal antibody produced in this study will enhance CMV monitoring and contribute to prevention of the spread of CMV infection which is spreading in yamCucumber mosaic virus (CMV) genus Cucumovirus was recently detected in yam in Ghana, Togo and Benin bringing to six the total number of countries reporting CMV infection in yam worldwide. Two serotypes of CMV are distinguished and a specific antibody against the yam isolate of CMV is currently not available. Rabbit polyclonal antibodies were produced against purified preparations of a yam isolate of CMV from Nigeria. The antibody titre was determined by Protein-A sandwich (PAS) enzymelinked immunosorbent assay (ELISA) and antigen-coated plate (ACP) ELISA. Antigen detection limit of the antibody was determined by PAS-ELISA using serial dilutions of infected sap. The CMV antiserum produced had a titre of 1:25,600 and 1:64,000 by PAS- and ACP-ELISA, respectively and a sap dilution end point of 1:160. The antibody detected homologous antigen in infected yam leaves from Ghana, Togo, Benin and Nigeria. The CMV polyclonal antibody produced in this study will enhance CMV monitoring and contribute to prevention of the spread of CMV infection which is spreading in ya

Production of Polyclonal Antibody Against an Isolate of Yam-infecting Badnavirus from Nigeria

Integrated viral sequences and high sequence variability among badnaviruses complicates the development of specific reliable molecular detection tests for yam-infecting badnaviruses. Thus Serological techniques are of notable importance for routine testing and monitoring of these viruses. The major limiting factor to the use of serological techniques is the limited availability of antibodies. Rabbit polyclonal antibody was produced against a purified preparation of a yam-infecting badnavirus from Nigeria. Antibody titre was determined by Protein-A sandwich (PAS) enzyme-linked immunosorbent assay (ELISA). The antibody produced had a titre of 1:1280 in PAS-ELISA and detected yam-infecting badnaviruses in infected yam leaves from Nigeria, Ghana, Benin and Togo. The suitability of the antibody for use in immunocapture polymerase chain reaction (IC-PCR) was evaluated. The antibody successfully trapped both Dioscorea alata bacilliform virus (DaBV) and Dioscorea sansibarensis bacilliform virus (DsBV) for IC-PCR detection. The antibody produced in this study will enhance certification of yam planting materials across West Africa and also facilitate the safe international movement of yam germplasm