28,582 research outputs found
Simple Model for Active Isolation of Machine Foundations by Open Trenches
Ground disturbance due to waves generated by a machine foundation can be detrimental to adjacent structures or operation of sensitive equipment nearby. For machine foundations vibrating at moderate to high frequencies, the amplitude of ground motion can be reduced significantly by installing a wave barrier around the source. A three-dimensional boundary element algorithm incorporating quadratic elements has been used to perform an extensive parametric study on the effectiveness of open trenches as wave barriers. Based on the results of the study, a simple model in the form of an algebraic expression is developed for estimating the vibration screening effectiveness of open trench wave barriers. Furthermore, through comparisons with published field test data and rigorous boundary element solutions, the validity of the simple model is established
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Controlled Release of Vancomycin and Tigecycline from an Orthopaedic Implant Coating Prevents Staphylococcus aureus Infection in an Open Fracture Animal Model.
Introduction:Treatment of open fractures routinely involves multiple surgeries and delayed definitive fracture fixation because of concern for infection. If implants were made less susceptible to infection, a one-stage procedure with intramedullary nailing would be more feasible, which would reduce morbidity and improve outcomes. Methods:In this study, a novel open fracture mouse model was developed using Staphylococcus aureus (S. aureus) and single-stage intramedullary fixation. The model was used to evaluate whether implants coated with a novel "smart" polymer coating containing vancomycin or tigecycline would be colonized by bacteria in an open fracture model infected with S. aureus. In vivo bioluminescence, ex vivo CFUs, and X-ray images were evaluated over a 42-day postoperative period. Results:We found evidence of a markedly decreased bacterial burden with the local release of vancomycin and tigecycline from the PEG-PPS polymer compared to polymer alone. Vancomycin was released in a controlled fashion and maintained local drug concentrations above the minimum inhibition concentration for S. aureus for greater than 7 days postoperatively. Bacteria were reduced 139-fold from implants containing vancomycin and undetected from the bone and soft tissue. Tigecycline coatings led to a 5991-fold reduction in bacteria isolated from bone and soft tissue and 15-fold reduction on the implants compared to polymer alone. Antibiotic coatings also prevented osteomyelitis and implant loosening as observed on X-ray. Conclusion:Vancomycin and tigecycline can be encapsulated in a polymer coating and released over time to maintain therapeutic levels during the perioperative period. Our results suggest that antibiotic coatings can be used to prevent implant infection and osteomyelitis in the setting of open fracture. This novel open fracture mouse model can be used as a powerful in vivo preclinical tool to evaluate and optimize the treatment of open fractures before further studies in humans
Sensitive Chemical Compass Assisted by Quantum Criticality
The radical-pair-based chemical reaction could be used by birds for the
navigation via the geomagnetic direction. An inherent physical mechanism is
that the quantum coherent transition from a singlet state to triplet states of
the radical pair could response to the weak magnetic field and be sensitive to
the direction of such a field and then results in different photopigments in
the avian eyes to be sensed. Here, we propose a quantum bionic setup for the
ultra-sensitive probe of a weak magnetic field based on the quantum phase
transition of the environments of the two electrons in the radical pair. We
prove that the yield of the chemical products via the recombination from the
singlet state is determined by the Loschmidt echo of the environments with
interacting nuclear spins. Thus quantum criticality of environments could
enhance the sensitivity of the detection of the weak magnetic field.Comment: 4 pages, 3 figure
Functional porous composites by blending with solution-processable molecular pores
Porous scrambled cages can be homogenously blended with both functional molecules and non-porous polymers to form functional porous composites materials.</p
Dispersive wave runup on non-uniform shores
Historically the finite volume methods have been developed for the numerical
integration of conservation laws. In this study we present some recent results
on the application of such schemes to dispersive PDEs. Namely, we solve
numerically a representative of Boussinesq type equations in view of important
applications to the coastal hydrodynamics. Numerical results of the runup of a
moderate wave onto a non-uniform beach are presented along with great lines of
the employed numerical method (see D. Dutykh et al. (2011) for more details).Comment: 8 pages, 6 figures, 18 references. This preprint is submitted to
FVCA6 conference proceedings. Other author papers can be downloaded at
http://www.lama.univ-savoie.fr/~dutykh
The FGK formalism for black p-branes in d dimensions
We present a generalization to an arbitrary number of spacetime (d) and
worldvolume (p+1) dimensions of the formalism proposed by Ferrara, Gibbons and
Kallosh to study black holes (p=0) in d=4 dimensions. We include the special
cases in which there can be dyonic and self- or anti-self-dual black branes.
Most of the results valid for 4-dimensional black holes (relations between
temperature, entropy and non-extremality parameter, and between entropy and
black-hole potential on the horizon) are straightforwardly generalized.
We apply the formalism to the case of black strings in N=2,d=5 supergravity
coupled to vector multiplets, in which the black-string potential can be
expressed in terms of the dual central charge and work out an explicit example
with one vector multiplet, determining supersymmetric and non-supersymmetric
attractors and constructing the non-extremal black-string solutions that
interpolate between them.Comment: 28 pages no figures; v2: some references adde
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