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It is well known that internal or molecular noise induces concentration oscillations in chemical systems whose deterministic models exhibit damped oscillations. In this article we show, using the linear-noise approximation of the chemical master equation, that noise can also induce oscillations in systems whose deterministic descriptions admit no damped oscillations, i.e., systems with a stable node. This non-intuitive phenomenon is remarkable since, unlike noise-induced oscillations in systems with damped deterministic oscillations, it cannot be explained by noise excitation of the deterministic resonant frequency of the system. We here prove the following general properties of stable-node noise-induced oscillations for systems with two species: (i) the upper bound of their frequency is given by the geometric mean of the real eigenvalues of the Jacobian of the system, (ii) the upper bound of the Q-factor of the oscillations is inversely proportional to the distance between the real eigenvalues of the Jacobian, and (iii) these oscillations are not necessarily exhibited by all interacting chemical species in the system. The existence and properties of stable-node oscillations are verified by stochastic simulations of the Brusselator, a cascade Brusselator reaction system, and two other simple chemical systems involving auto-catalysis and trimerization. It is also shown how external noise induces stable node oscillations with different properties than those stimulated by internal noise. [ABSTRACT FROM AUTHOR]

Classical percolation theory is concerned with the onset of geometrical connectivity and the accompanied onset of electrical connectivity in disordered systems. It was found, however, that in many systems, such as various composites, the geometrical and electrical onsets of the connectivity are not simultaneous and the correlation between them depends on physical processes such as tunneling. The difference between the above two types of systems and the consequences for the electrical transport properties of the latter composites have been largely ignored in the past. The application of scanning local probe microscopies and some recent theoretical developments have enabled a better understanding of the latter systems and their sometimes "strange" behavior as bona fide percolation systems. In this review we consider the above issues and their manifestation in three types of systems: Carbon Black–Polymer composites, metal–insulator cermets and hydrogenated microcrystalline silicon. [ABSTRACT FROM AUTHOR]

Duckweed (Lemnaceae) can support the development of freshwater aquaculture if used as extractive species in Integrated MultiTrophic Aquaculture (IMTA) systems. These aquatic plants have the advantage of producing protein-rich biomass that has several potential uses. On the contrary, other biological compartments, such as microalgae and bacteria, present in the water and competing with duckweed for light and nutrients cannot be harvested easily from the water. Moreover, as phytoplankton cannot easily be harvested, nutrients are eventually re-released; hence, this compartment does not contribute to the overall water remediation process. In the present study, a mesocosm experiment was designed to quantify the portion of nutrients effectively removed by duckweed in a duckweed-based aquaculture wastewater remediation system. Three tanks were buried next to a pilot-scale IMTA system used for the production of rainbow trout and perch. The tanks received aquaculture effluents from the adjacent system, and 50% of their surface was covered by duckweed. Daily water analyses of samples at the inlet and outlet of the mesocosm allowed quantification of the amount of nutrients removed in total. The portion removed by duckweed was determined by examining the nutrient content in the initial and final biomass. The portion of nutrients removed by other compartments was similarly estimated. The results show that duckweed is responsible for the removal of 31% and 29% of N and P, respectively. Phytoplankton removed 33% and 38% of N and P, respectively, while the biofilm played no major role in nutrient removal. The remainder of the removed nutrients were probably assimilated by bacteria or sedimented. It is speculated that a higher initial duckweed density can limit phytoplankton growth and, therefore, increase the portion of nutrients removed by the duckweed compartment.

The aquaculture industry is considered a key sector for the supply of high quality, nutritious food. However, growth of the aquaculture sector has been slow, particularly in Europe, and this is amongst others linked to concerns about environmental impacts of this industry. Integrated Multitrophic Aquaculture (IMTA) has been identified as an important technology to sustainably improve freshwater fish production. In IMTA, economically valuable extractive species feed on waste produced by other species, remediating wastewater, and minimising the environmental impact of aquaculture. This study presents quantitative information on the nitrogen and phosphorus removal efficiency of a duckweed-based, pilot, semi-commercial IMTA system. Duckweed species are free-floating freshwater species belonging to the family of Lemnaceae. The aim of this study was to test the potential of duckweed-based IMTA under realistic environmental conditions. Three different approaches were used to assess remediation capacity; 1) assessment of water quality pre and post treatment with duckweed showed that the system can remove 0.78 and 0.38 T y -1 of Total Nitrogen (TN) and Total Phosphorus (TP), respectively 2) based on nitrogen and phosphorus content of newly grown duckweed biomass, it was shown that 1.71 and 0.22 T y -1 of TN and TP can be removed, respectively 3) extrapolation based on laboratory established nitrogen and phosphorus uptake rates determined that 0.88 and 0.08 T y -1 of TN and TP can be removed by the system. There is substantive agreement between the three assessments, and the study confirms that duckweed can maintain good quality water in an IMTA system, while yielding high protein content (21.84 ± 2.45%) biomass. The quantitative data on nitrogen and phosphorus removal inform the design of further IMTA systems, and especially create a scientific basis to determine the balance between aquaculture and extractive species., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: To determine parental satisfaction and cost-effectiveness of having a frenotomy performed in the office setting versus in the operating room under general anesthesia., Method: After obtaining IRB approval at The Children's Hospital of Philadelphia (CHOP), we performed a retrospective chart review of patients having a frenotomy in the office between 2003-2008. 55 patients met the criteria and 25 were consented and their parents interviewed., Conclusion: All participants reported an improvement in feeding within one day and up to two weeks following the procedure. Parents also reported being somewhat satisfied to very satisfied with having the frenotomy performed in the office versus under general anesthesia. There were no complications reported. Performing the frenotomy in the office provided patients with satisfaction as well as cost savings. The surgical fee for a frenotomy in the office is $850 and is the same as if the procedure is performed in the operating room. Performing a frenotomy under general anesthesia includes extra cost which consists of an anesthesia fee of $500-$900 and hospital charges ranging from $500-$8,000. Performing the frenotomy in the office on our 25 patients has resulted in a cost savings of more than $240,000 and the avoidance of general anesthesia in the first few weeks of life. Office frenotomy should be considered in children with ankyloglossia who present with difficulty nursing in the first week of life.

Sylgard((R)) is a biocompatible elastomer which has been widely used in biomedical applications including in simulations of the mechanical response of soft tissues and mechanotransduction investigations. In this study the effect of fabrication parameters including base to curing agent ratio and curing time on the mechanical response of Sylgard((R)) was investigated and a novel fabrication technique for the production of mock arteries with highly uniform thickness, which is essential for mechanotransduction studies, is described. Finally a method for the surface treatment of Sylgard((R)) using sulphuric acid and fibronectin to enhance smooth muscle cell (SMC) adhesion is proposed and examined in vitro. Sylgard((R)) mock coronary arteries fabricated using the proposed technique exhibited a mechanical response close to arterial tissue with cell adhesion enhanced using the surface treatment techniques described.

Intracoronary stent implantation is a mechanical procedure, the success of which depends to a large degree on the mechanical properties of each vessel component involved and the pressure applied to the balloon. Little is known about the influence of plaque composition on arterial overstretching and the subsequent injury to the vessel wall following stenting. An idealised finite element model was developed to investigate the influence of both plaque types (hypercellular, hypocellular and calcified) and stent inflation pressures (9, 12 and 15 atm) on vessel and plaque stresses during the implantation of a balloon expandable coronary stent into an idealised stenosed artery. The plaque type was found to have a significant influence on the stresses induced within the artery during stenting. Higher stresses were predicted in the artery wall for cellular plaques, while the stiffer calcified plaque appeared to play a protective role by reducing the levels of stress within the arterial tissue for a given inflation pressure. Higher pressures can be applied to calcified plaques with a lower risk of arterial vascular injury which may reduce the stimulus for in-stent restenosis. Results also suggest that the risk of plaque rupture, and any subsequent thrombosis due to platelet deposition at the fissure, is greater for calcified plaques with low fracture stresses.