407 research outputs found
Implantable Wireless Systems: A Review of Potentials and Challenges
With the current advancement in micro-and nano-fabrication processes and the newly developed approaches, wireless implantable devices are now able to meet the demand for compact, self-powered, wireless, and long-lasting implantable devices for medical and health-care applications. The demonstrated fabrication advancement enabled the wireless implantable devices to overcome the previous limitations of electromagnetic-based wireless devices such as the high volume due to large antenna size and to overcome the tissue and bone losses related to the ultrasound implantable devices. Recent state-of-the-are wireless implantable devices can efficiently harvest electromagnetic energy and detect RF signals with minimum losses. Most of the current implanted devices are powered by batteries, which is not an ideal solution as these batteries need periodic charging and replacement. On the other hand, the implantable devices that are powered by energy harvesters are operating continuously, patient-friendly, and are easy to use. Future wireless implantable devices face a strong demand to be linked with IoT-based applications and devices with data visualization on mobile devices. This type of application requires additional units, which means more power consumption. Thus, the challenge here is to reduce the overall power consumption and increase the wireless power transfer efficiency. This chapter presents the state-of-the-art wireless power transfer techniques and approaches that are used to drive implantable devices. These techniques include inductive coupling, radiofrequency, ultrasonic, photovoltaic, and heat. The advantages and disadvantages of these approaches and techniques along with the challenges and limitations of each technique will be discussed. Furthermore, the performance parameters such as operating distance, energy harvesting efficiency, and size will be discussed and analyzed to introduce a comprehensive comparison. Finally, the recent advances in materials development and wireless communication strategies, are also discussed
Continuous macroscopic limit of a discrete stochastic model for interaction of living cells
In the development of multiscale biological models it is crucial to establish
a connection between discrete microscopic or mesoscopic stochastic models and
macroscopic continuous descriptions based on cellular density. In this paper a
continuous limit of a two-dimensional Cellular Potts Model (CPM) with excluded
volume is derived, describing cells moving in a medium and reacting to each
other through both direct contact and long range chemotaxis. The continuous
macroscopic model is obtained as a Fokker-Planck equation describing evolution
of the cell probability density function. All coefficients of the general
macroscopic model are derived from parameters of the CPM and a very good
agreement is demonstrated between CPM Monte Carlo simulations and numerical
solution of the macroscopic model. It is also shown that in the absence of
contact cell-cell interactions, the obtained model reduces to the classical
macroscopic Keller-Segel model. General multiscale approach is demonstrated by
simulating spongy bone formation from loosely packed mesenchyme via the
intramembranous route suggesting that self-organizing physical mechanisms can
account for this developmental process.Comment: 4 pages, 3 figure
The pulsating DA white dwarf star EC 14012-1446: results from four epochs of time-resolved photometry
The pulsating DA white dwarfs are the coolest degenerate stars that undergo
self-driven oscillations. Understanding their interior structure will help to
understand the previous evolution of the star. To this end, we report the
analysis of more than 200 h of time-resolved CCD photometry of the pulsating DA
white dwarf star EC 14012-1446 acquired during four observing epochs in three
different years, including a coordinated three-site campaign. A total of 19
independent frequencies in the star's light variations together with 148
combination signals up to fifth order could be detected. We are unable to
obtain the period spacing of the normal modes and therefore a mass estimate of
the star, but we infer a fairly short rotation period of 0.61 +/- 0.03 d,
assuming the rotationally split modes are l=1. The pulsation modes of the star
undergo amplitude and frequency variations, in the sense that modes with higher
radial overtone show more pronounced variability and that amplitude changes are
always accompanied by frequency variations. Most of the second-order
combination frequencies detected have amplitudes that are a function of their
parent mode amplitudes, but we found a few cases of possible resonantly excited
modes. We point out the complications in the analysis and interpretation of
data sets of pulsating white dwarfs that are affected by combination
frequencies of the form f_A+f_B-f_C intruding into the frequency range of the
independent modes.Comment: 14 pages, 6 figures, 6 tables. MNRAS, in pres
Heat Shock Protein 70 Prevents both Tau Aggregation and the Inhibitory Effects of Preexisting Tau Aggregates on Fast Axonal Transport
Aggregation and accumulation of the microtubule-associated protein tau are associated with
cognitive decline and neuronal degeneration in Alzheimer's disease and other tauopathies. Thus,
preventing the transition of tau from a soluble state to insoluble aggregates and/or reversing the
toxicity of existing aggregates would represent a reasonable therapeutic strategy for treating these
neurodegenerative diseases. Here we demonstrate that molecular chaperones of the heat shock
protein 70 (Hsp70) family are potent inhibitors of tau aggregation in vitro, preventing the
formation of both mature fibrils and oligomeric intermediates. Remarkably, addition of Hsp70 to a
mixture of oligomeric and fibrillar tau aggregates prevents the toxic effect of these tau species on
fast axonal transport, a critical process for neuronal function. When incubated with preformed tau
aggregates, Hsp70 preferentially associated with oligomeric over fibrillar tau, suggesting that
prefibrillar oligomeric tau aggregates play a prominent role in tau toxicity. Taken together, our
data provide a novel molecular basis for the protective effect of Hsp70 in tauopathies
Pathogenic forms of tau inhibit kinesin-dependent axonal transport through a mechanism involving activation of axonal phosphotransferases
© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Neuroscience 31 (2011): 9858-9868, doi:10.1523/JNEUROSCI.0560-11.2011.Aggregated filamentous forms of hyperphosphorylated tau (a microtubule-associated protein) represent pathological hallmarks of Alzheimer's disease (AD) and other tauopathies. While axonal transport dysfunction is thought to represent a primary pathogenic factor in AD and other neurodegenerative diseases, the direct molecular link between pathogenic forms of tau and deficits in axonal transport remain unclear. Recently, we demonstrated that filamentous, but not soluble, forms of wild-type tau inhibit anterograde, kinesin-based fast axonal transport (FAT) by activating axonal protein phosphatase 1 (PP1) and glycogen synthase kinase 3 (GSK3), independent of microtubule binding. Here, we demonstrate that amino acids 2–18 of tau, comprising a phosphatase-activating domain (PAD), are necessary and sufficient for activation of this pathway in axoplasms isolated from squid giant axons. Various pathogenic forms of tau displaying increased exposure of PAD inhibited anterograde FAT in squid axoplasm. Importantly, immunohistochemical studies using a novel PAD-specific monoclonal antibody in human postmortem tissue indicated that increased PAD exposure represents an early pathogenic event in AD that closely associates in time with AT8 immunoreactivity, an early marker of pathological tau. We propose a model of pathogenesis in which disease-associated changes in tau conformation lead to increased exposure of PAD, activation of PP1-GSK3, and inhibition of FAT. Results from these studies reveal a novel role for tau in modulating axonal phosphotransferases and provide a molecular basis for a toxic gain-of-function associated with pathogenic forms of tau.This work was supported by NIH Grants T32 AG020506-07 (N.M.K.); AG09466 (L.I.B.); and NS23868, NS23320,
and NS41170 (S.T.B.); as well as 2007/2008 MBL Summer Research Fellowships and an ALS/CVS Therapy Alliance
grant (G.M.)
Extra corporal membrane oxygenation in general thoracic surgery: a new single veno-venous cannulation
Extracorporeal membrane oxygenation (ECMO) is used in severe respiratory failure to maintain adequate gas exchange. So far, this technique has not been commonly used in general thoracic surgery. We present a case using ECMO for peri-operative airway management for pulmonary resection, using a novel single-site, internal jugular, veno-venous ECMO cannula
- …