Broad dissemination of plasmid-mediated quinolone resistance genes in sediments of two urban coastal wetlands

Contamination of soil and water with antibiotic-resistant bacteria may create reservoirs of antibiotic resistance genes that have the potential to negatively impact future public health through horizontal gene transfer. The plasmid-mediated quinolone resistance genes qnrA, qnrB, qnrS, qepA, and aac(6')-Ib-cr were detected by PCR amplification of metagenomic DNA from surface sediments of the Tijuana River Estuary, a sewage-impacted coastal wetland along the U.S.-Mexico border; sediments of Famosa Slough, a nearby urban wetland that is largely unaffected by sewage, contained only qnrB, qnrS, and qepA. The number of PCR-positive sites and replicates increased in both wetlands after rainfall. Real-time quantitative PCR revealed a significant increase (p < 0.0005) in qnrA abundance (copies per gram sediment or per 16S rDNA copy) in Tijuana River Estuary sediments immediately following rainfall, but no significant change was measured at Famosa Slough (p > 0.1). Nucleotide sequences of cloned qnrA amplicons were all affiliated with qnrA genes found on plasmids of clinical isolates with one exception that was most similar to the chromosomal qnrA gene found in Shewanella algae. Our results suggest that urban wetlands may become reservoirs of antibiotic resistance genes, particularly where wastewater is improperly managed.     

Geometric optimization of a thermoacoustic regenerator

This work illustrates the optimization of thermoacoustic systems, while taking into account thermal losses to the surroundings that are typically disregarded. A simple thermoacoustic engine is used as an example for the methodology. Its driving component, the thermoacoustic regenerator (also referred to as the stack), is modeled with a finite element method and its dimensions are varied to find an optimal design with regard to thermal losses. Thermoacoustic phenomena are included by considering acoustic power, and viscous and capacitive losses that are characteristic for the regenerator. The optimization considers four weighted objectives and is conducted with the Nelder–Mead Simplex method. When trying to minimize thermal losses, the presented results show that the regenerator should be designed to be as short as possible. It was found that there is an optimal regenerator diameter for a given length. The results are presented for a variety of materials and weights for each objective.     

Unsteady transverse injection of kerosene into a supersonic flow

A shadowgraph and a new fuel injection system were used to study kerosene transversely injected into a supersonic flow. High pressure and velocity of injection can be attained. The pressure time histories were detected in oil-line and the shadowgraphs of the flow field were obtained at different time-delays. The inflow stagnation pressure was varied to change the local flow speed in test section. The results indicate that kerosene jet exhibits deep penetration and four regimes appear clearly during the fuel jet atomization in a high-speed flow. The jet disintegration is caused by surface waves propagating along the jet surface, and the breakup point is located at the wave trough. The surface waves are dominantly generated by aerodynamic force. The jet shock is close to windward surface of the jet. The shock reflects on and transmits in duct boundary layers. In the case of unsteady injection, the shock structure is very complicated and different from that of hydrogen injection. The results of kerosene inj     

Electrochemically Driven Hydroxyapatite Nanoparticles Coating of Medical Implants

Calcium phosphates are of great interest for biomedical applications such as bone tissue engineering, bone fillers, drug and gene delivery, and orthopedic and dental implant coating. Here, the first electrochemically driven coating of medical implants using hydroxyapatite (HAp) nanoparticles (NPs) as building blocks is reported. This uncommon combination offers a simple, straightforward, and economic process with well controllable, pure, single‐phase HAp. Crystalline, pure HAp NPs are formed by precipitation reaction. The HAp NPs are dispersed by either citrate or poly(acrylic acid) to form pH sensitive dispersion. Controllable and homogeneous coating of medical implants is accomplished by altering the pH on the surface upon applying either a constant potential or current. The process involves protonation of the carboxylic acid moieties, which causes the irreversible aggregation of the HAp NPs due to diminishing the repulsive forces between the particles. Deposition is further demonstrated on a commercial dental implant. Moreover, the adhesion of the coating satisfies FDA and international standard requirements. A porous interconnected network of bone‐like HAp layer is formed during soaking in a simulated body fluid for 30 d and is similar to bone generation, and it therefore holds promise for further in vivo testing.     

A very low-noise receiver for 80–120 GHz

A new dual-polarized cryogenic Schottky barrier mixer receiver for radio astronomy applications is described. Between 85 and 120 GHz, the double sideband receiver temperature, including all contributions from the polarization diplexing system, telescope coupling optics and dewar window is less than 125°K in either channel. Novel features include a very broadband, fixed tuned mixer design and a compact, low-loss, linear polarization diplexing scheme.     

Comparing women and men: What is being compared and why?

Comments on A. H. Eagly's (see record 1995-21141-001) discussion comparing the sexes in scientific research. The author presents and discusses 2 issues that arose from Eagly's overview. The 1st issue concerns the database underlying the meta-analytic summaries and asks exactly what is being compared. The 2nd issue concerns the relative magnitude of the sex differences and also asks why men and women, rather than other social groups, should be compared. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Expression and localization in the fish retina of a homologue of the Alzheimer's related PS1 gene

Early-onset familial Alzheimer's disease (early-onset FAD) has been linked with mutations in the presenilin gene, PS1. Mutations in PS1 may affect the processing/trafficking of b-amyloid precursor-protein (bAPP) and favour the production of toxic amyloid-b fragments that are associated with neural degeneration. This study reports the expression of a PS1-like cDNA in the carp (Cyprinus carpio) retina (the encoded protein shows 76% identity to the human PS1 protein). Carp PS1 mRNA was localized by in situ hybridization to the photoreceptor cell, inner nuclear and ganglion cell layers. Expression of the PS1 gene in the rat retina was also confirmed. The retinal expression of PS1 raises the possibility that PS1 mutations also lead to neural degeneration in the retina.     

Evaluation of the effect of processing on sunflower protein quality

The protein quality of sunflower meal, sampled at different processing steps, was studied. The protein quality was evaluated in terms of the ‘available lysine’ by the modified Carpenter method, and the biological value (BV) was determined by the Tetrahymena pyriformis test. The samples obtained from two oil expressors showed little change during processing, as assessed by two analytical methods. Sunflower meal heated at 110°C for various periods showed a decrease in available lysine from 3·4% to 0·9%.     

The effect of electrolytes on direct dyes for cotton

Electrolytes generally promote dyebath exhaustion when direct dyes are used for cellulosic fibers, but the extent with which they do so usually varies from one electrolyte to another. Two direct dyes with varying numbers of sulfonic acid groups were investigated. Cotton cellulose was dyed with these dyes using different electrolytes and a phosphate buffer system. The relationship between strength loss with increase in number of sulfonic acid groups was an obvious observation. Wash fastness results had indicated that the most important consideration is the molecular weight and the overall molecular architecture of the dye.