A mathematical model for electrical stimulation of a monolayer of cardiac cells

BACKGROUND: The goal of our study is to examine the effect of stimulating a two-dimensional sheet of myocardial cells. We assume that the stimulating electrode is located in a bath perfusing the tissue. METHODS: An equation governing the transmembrane potential, based on the continuity equation and Ohm's law, is solved numerically using a finite difference technique. RESULTS: The sheet is depolarized under the stimulating electrode and is hyperpolarized on each side of the electrode along the fiber axis. CONCLUSIONS: The results are similar to those obtained previously by Sepulveda et al. (Biophys J, 55: 987–999, 1989) for stimulation of a two-dimensional sheet of tissue with no perfusing bath present

Mercury Removal from Concentrated Sulfuric Acid by Electrochemical Alloy Formation on Platinum

Mercury is a highly toxic heavy metal, and improved removal processes are required in a range of industrial applications to limit the environmental impacts. At present, no viable removal methods exist commercially for mercury removal of aqueous solutions at high acidic conditions, such as concentrated sulfuric acid. Herein, we show that electrochemical mercury removal based on electrochemical alloy formation on platinum, forming PtHg4, can be used to remove mercury from concentrated sulfuric acid. Thin platinum film electrodes and porous electrodes with supported platinum are used to remove more than 90% of mercury from concentrated acid from a zinc smelter with an initial mercury concentration of 0.3-0.9 mg/kg, achieving high-quality acid (<0.08 mg/kg) within 80 h. The removal process is carried out in 50 mL laboratory-scale experiments and scaled up to a 20 L pilot reactor with retained removal efficiency, highlighting excellent scalability of the method. In addition, the removal efficiency and stability of different electrode substrate materials are studied to ensure high-quality acid and a long lifetime of the electrodes in harsh chemical conditions, offering a potential method for future large-scale mercury decontamination of sulfuric acid

Conductivity Imaging in Plates Using Current Injection Tomography

The task of reconstructing an unknown distribution of electrical conductivity is widely recognized as a central theoretical problem in eddy-current nondestructive evaluation [1]. Rather than using an eddy-current method, we address this problem using DC injection of current into conductive materials. Experimental methods of the magnetic imaging of injected currents using high-resolution SQUID magnetometers have been described elsewhere [2]. In this paper we describe a tomographic method for using magnetically-imaged, injected currents to reconstruct distributions of electrical conductivity. Much of what we describe should also be applicable to data obtained using uniform colinear eddy currents induced by means of planar sheet inducers [4, 5]

Temperature and concentration dependence of the electrochemical PtHg4 alloy formation for mercury decontamination

New and improved methods to remove toxic mercury from contaminated waters and waste streams are highly sought after. Recently, it was shown that electrochemical alloy formation of PtHg4 on a platinum surface with mercury ions from solution can be utilized for decontamination, with several advantages over conventional techniques. Herein, we examine the alloy formation process in more detail by mercury concentration measurements using inductively coupled plasma mass spectrometry in batch measurements as well as electrochemical quartz crystal microbalance analysis both in batch and in flowing water with initial mercury concentrations ranging from 0.25 to 75000 \ub5g L−1 Hg2+. Results show that mercury is effectively removed from all solutions and the rate of alloy formation is constant over time, as well as for very thick layers of PtHg4. The apparent activation energy for the electrochemical alloy formation was determined to be 0.29 eV, with a reaction order in mercury ion concentration around 0.8. The obtained results give new insights that are vital in the assessment and further development of electrochemical alloy formation as a method for large scale mercury decontamination

Quantifying the effect of uncertainty in input parameters in a simplified bidomain model of partial thickness ischaemia

Reduced blood flow in the coronary arteries can lead to damaged heart tissue (myocardial ischaemia). Although one method for detecting myocardial ischaemia involves changes in the ST segment of the electrocardiogram, the relationship between these changes and subendocardial ischaemia is not fully understood. In this study, we modelled ST-segment epicardial potentials in a slab model of cardiac ventricular tissue, with a central ischaemic region, using the bidomain model, which considers conduction longitudinal, transverse and normal to the cardiac fibres. We systematically quantified the effect of uncertainty on the input parameters, fibre rotation angle, ischaemic depth, blood conductivity and six bidomain conductivities, on outputs that characterise the epicardial potential distribution. We found that three typical types of epicardial potential distributions (one minimum over the central ischaemic region, a tripole of minima, and two minima flanking a central maximum) could all occur for a wide range of ischaemic depths. In addition, the positions of the minima were affected by both the fibre rotation angle and the ischaemic depth, but not by changes in the conductivity values. We also showed that the magnitude of ST depression is affected only by changes in the longitudinal and normal conductivities, but not by the transverse conductivities

Three applications of path integrals: equilibrium and kinetic isotope effects, and the temperature dependence of the rate constant of the [1,5] sigmatropic hydrogen shift in (Z)-1,3-pentadiene

Recent experiments have confirmed the importance of nuclear quantum effects even in large biomolecules at physiological temperature. Here we describe how the path integral formalism can be used to describe rigorously the nuclear quantum effects on equilibrium and kinetic properties of molecules. Specifically, we explain how path integrals can be employed to evaluate the equilibrium (EIE) and kinetic (KIE) isotope effects, and the temperature dependence of the rate constant. The methodology is applied to the [1,5] sigmatropic hydrogen shift in pentadiene. Both the KIE and the temperature dependence of the rate constant confirm the importance of tunneling and other nuclear quantum effects as well as of the anharmonicity of the potential energy surface. Moreover, previous results on the KIE were improved by using a combination of a high level electronic structure calculation within the harmonic approximation with a path integral anharmonicity correction using a lower level method.Comment: 9 pages, 4 figure

A Highly Conserved Program of Neuronal Microexons Is Misregulated in Autistic Brains

SummaryAlternative splicing (AS) generates vast transcriptomic and proteomic complexity. However, which of the myriad of detected AS events provide important biological functions is not well understood. Here, we define the largest program of functionally coordinated, neural-regulated AS described to date in mammals. Relative to all other types of AS within this program, 3-15 nucleotide “microexons” display the most striking evolutionary conservation and switch-like regulation. These microexons modulate the function of interaction domains of proteins involved in neurogenesis. Most neural microexons are regulated by the neuronal-specific splicing factor nSR100/SRRM4, through its binding to adjacent intronic enhancer motifs. Neural microexons are frequently misregulated in the brains of individuals with autism spectrum disorder, and this misregulation is associated with reduced levels of nSR100. The results thus reveal a highly conserved program of dynamic microexon regulation associated with the remodeling of protein-interaction networks during neurogenesis, the misregulation of which is linked to autism

The SNAPSHOT study protocol : SNAcking, Physical activity, Self-regulation, and Heart rate Over Time

Peer reviewedPublisher PD

How are falls and fear of falling associated with objectively measured physical activity in a cohort of community-dwelling older men?

BACKGROUND: Falls affect approximately one third of community-dwelling older adults each year and have serious health and social consequences. Fear of falling (FOF) (lack of confidence in maintaining balance during normal activities) affects many older adults, irrespective of whether they have actually experienced falls. Both falls and fear of falls may result in restrictions of physical activity, which in turn have health consequences. To date the relation between (i) falls and (ii) fear of falling with physical activity have not been investigated using objectively measured activity data which permits examination of different intensities of activity and sedentary behaviour. METHODS: Cross-sectional study of 1680 men aged 71-92 years recruited from primary care practices who were part of an on-going population-based cohort. Men reported falls history in previous 12 months, FOF, health status and demographic characteristics. Men wore a GT3x accelerometer over the hip for 7 days. RESULTS: Among the 12% of men who had recurrent falls, daily activity levels were lower than among non-fallers; 942 (95% CI 503, 1381) fewer steps/day, 12(95% CI 2, 22) minutes less in light activity, 10(95% CI 5, 15) minutes less in moderate to vigorous PA [MVPA] and 22(95% CI 9, 35) minutes more in sedentary behaviour. 16% (n = 254) of men reported FOF, of whom 52% (n = 133) had fallen in the past year. Physical activity deficits were even greater in the men who reported that they were fearful of falling than in men who had fallen. Men who were fearful of falling took 1766(95% CI 1391, 2142) fewer steps/day than men who were not fearful, and spent 27(95% CI 18, 36) minutes less in light PA, 18(95% CI 13, 22) minutes less in MVPA, and 45(95% CI 34, 56) minutes more in sedentary behaviour. The significant differences in activity levels between (i) fallers and non-fallers and (ii) men who were fearful of falling or not fearful, were mediated by similar variables; lower exercise self-efficacy, fewer excursions from home and more mobility difficulties. CONCLUSIONS: Falls and in particular fear of falling are important barriers to older people gaining health benefits of walking and MVPA. Future studies should assess the longitudinal associations between falls and physical activity

Extensive arterial and venous thrombo-embolism with chemotherapy for testicular cancer: a case report

Germ cell tumours tend to affect young adults and with advanced treatments achieve more than 90% cure rates. Over the years cisplatin has significantly improved the relapse free survival in these patients, hence forming an essential component of chemotherapy regimes. But, the thrombo-embolic complications suffered with cisplatin significantly affect the quality of life in these young patients