Design of a laminar-flow-control supercritical airfoil for a swept wing

An airfoil was analytically designed and analyzed for a combination of supercritical flow and laminar flow control (LFC) by boundary layer suction. A shockless inverse method was used to design an airfoil and an analysis method was used in lower surface redesign work. The laminar flow pressure distributions were computed without a boundary layer under the assumption that the laminar boundary layer would be kept thin by suction. Inviscid calculations showed that this 13.5 percent thick airfoil has shockless flows for conditions at and below the design normal Mach number of 0.73 and the design section lift coefficient of 0.60, and that the maximum local normal Mach number is 1.12 at the design point. The laminar boundary layer instabilities can be controlled with suction but the undercut leading edge of the airfoil provides a low velocity, constant pressure coefficients region which is conducive to laminar flow without suction. The airfoil was designed to be capable of lift recovery with no suction by the deflection of a small trailing edge flap

Discrete--time ratchets, the Fokker--Planck equation and Parrondo's paradox

Parrondo's games manifest the apparent paradox where losing strategies can be combined to win and have generated significant multidisciplinary interest in the literature. Here we review two recent approaches, based on the Fokker-Planck equation, that rigorously establish the connection between Parrondo's games and a physical model known as the flashing Brownian ratchet. This gives rise to a new set of Parrondo's games, of which the original games are a special case. For the first time, we perform a complete analysis of the new games via a discrete-time Markov chain (DTMC) analysis, producing winning rate equations and an exploration of the parameter space where the paradoxical behaviour occurs.Comment: 17 pages, 5 figure

Influence of Visual Feedback On Dynamic Balance Control in Chronic Stroke Survivors

Chronic stroke survivors have an increased incidence of falls during walking, suggesting changes in dynamic balance control post-stroke. Despite this increased incidence of falls during walking, balance control is often studied only in standing. The purpose of this study was to quantify deficits in dynamic balance control during walking, and to evaluate the influence of visual feedback on this control in stroke survivors. Ten individuals with chronic stroke, and ten neurologically intact individuals participated in this study. Walking performance was assessed while participants walked on an instrumented split-belt treadmill with different types of visual feedback. Dynamic balance control was quantified using both the extent of center of mass (COM) movement in the frontal plane over a gait cycle (COM sway), and base of support (step width). Stroke survivors walked with larger COM sway and wider step widths compared to controls. Despite these baseline differences, both groups walked with a similar ratio of step width to COM sway (SW/COM). Providing a stationary target with a laser reference of body movement reduced COM sway only in the stroke group, indicating that visual feedback of sway alters dynamic balance control post-stroke. These results demonstrate that stroke survivors attempt to maintain a similar ratio of step width to COM movement, and visual cues can be used to help control COM movement during walking post-stroke

Solving large-scale dynamic systems using band Lanczos method in Rockwell NASTRAN on CRAY X-MP

The improved cost effectiveness using better models, more accurate and faster algorithms and large scale computing offers more representative dynamic analyses. The band Lanczos eigen-solution method was implemented in Rockwell's version of 1984 COSMIC-released NASTRAN finite element structural analysis computer program to effectively solve for structural vibration modes including those of large complex systems exceeding 10,000 degrees of freedom. The Lanczos vectors were re-orthogonalized locally using the Lanczos Method and globally using the modified Gram-Schmidt method for sweeping rigid-body modes and previously generated modes and Lanczos vectors. The truncated band matrix was solved for vibration frequencies and mode shapes using Givens rotations. Numerical examples are included to demonstrate the cost effectiveness and accuracy of the method as implemented in ROCKWELL NASTRAN. The CRAY version is based on RPK's COSMIC/NASTRAN. The band Lanczos method was more reliable and accurate and converged faster than the single vector Lanczos Method. The band Lanczos method was comparable to the subspace iteration method which was a block version of the inverse power method. However, the subspace matrix tended to be fully populated in the case of subspace iteration and not as sparse as a band matrix

Parrondo-like behavior in continuous-time random walks with memory

The Continuous-Time Random Walk (CTRW) formalism can be adapted to encompass stochastic processes with memory. In this article we will show how the random combination of two different unbiased CTRWs can give raise to a process with clear drift, if one of them is a CTRW with memory. If one identifies the other one as noise, the effect can be thought as a kind of stochastic resonance. The ultimate origin of this phenomenon is the same of the Parrondo's paradox in game theoryComment: 8 pages, 3 figures, revtex; enlarged and revised versio

When good bugs go bad: Epidemiology and antimicrobial resistance profiles of Corynebacterium striatum, an emerging multidrug-resistant, opportunistic pathogen

ABSTRACT Infections with Corynebacterium striatum have been described in the literature over the last 2 decades, with the majority being bacteremia, central line infections, and occasionally, endocarditis. In recent years, the frequency of C. striatum infections appears to be increasing; a factor likely contributing to this is the increased ease and accuracy of the identification of Corynebacterium spp., including C. striatum , from clinical cultures. The objective of this study was to retrospectively characterize C. striatum isolates recovered from specimens submitted as part of routine patient care at a 1,250-bed, tertiary-care academic medical center. Multiple strain types were recovered, as demonstrated by repetitive-sequence-based PCR. Most of the strains of C. striatum characterized were resistant to antimicrobials commonly used to treat Gram-positive organisms, such as penicillin, ceftriaxone, meropenem, clindamycin, and tetracycline. The MIC 50 for ceftaroline was &gt;32 μg/ml. Although there are no interpretive criteria for susceptibility with telavancin, it appeared to have potent in vitro efficacy against this species, with MIC 50 and MIC 90 values of 0.064 and 0.125 μg/ml, respectively. Finally, as previously reported in case studies, we demonstrated rapid in vitro development of daptomycin resistance in 100% of the isolates tested ( n = 50), indicating that caution should be exhibited when using daptomycin for the treatment of C. striatum infections. C. striatum is an emerging, multidrug-resistant pathogen that can be associated with a variety of infection types. </jats:p

Quantitative nucleotide level analysis of regulation of translation in response to depolarization of cultured neural cells

Studies on regulation of gene expression have contributed substantially to understanding mechanisms for the long-term activity-dependent alterations in neural connectivity that are thought to mediate learning and memory. Most of these studies, however, have focused on the regulation of mRNA transcription. Here, we utilized high-throughput sequencing coupled with ribosome footprinting to globally characterize the regulation of translation in primary mixed neuronal-glial cultures in response to sustained depolarization. We identified substantial and complex regulation of translation, with many transcripts demonstrating changes in ribosomal occupancy independent of transcriptional changes. We also examined sequence-based mechanisms that might regulate changes in translation in response to depolarization. We found that these are partially mediated by features in the mRNA sequence—notably upstream open reading frames and secondary structure in the 5′ untranslated region—both of which predict downregulation in response to depolarization. Translationally regulated transcripts are also more likely to be targets of FMRP and include genes implicated in autism in humans. Our findings support the idea that control of mRNA translation plays an important role in response to neural activity across the genome

Novel cruzain inhibitors for the treatment of Chagas' disease.

The protozoan parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, affects millions of individuals and continues to be an important global health concern. The poor efficacy and unfavorable side effects of current treatments necessitate novel therapeutics. Cruzain, the major cysteine protease of T. cruzi, is one potential novel target. Recent advances in a class of vinyl sulfone inhibitors are encouraging; however, as most potential therapeutics fail in clinical trials and both disease progression and resistance call for combination therapy with several drugs, the identification of additional classes of inhibitory molecules is essential. Using an exhaustive virtual-screening and experimental validation approach, we identify several additional small-molecule cruzain inhibitors. Further optimization of these chemical scaffolds could lead to the development of novel drugs useful in the treatment of Chagas' disease