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Nature Oct 2015The fast growth of information technology has been sustained by continuous scaling down of the silicon-based metal-oxide field-effect transistor. However, such...
The fast growth of information technology has been sustained by continuous scaling down of the silicon-based metal-oxide field-effect transistor. However, such technology faces two major challenges to further scaling. First, the device electrostatics (the ability of the transistor's gate electrode to control its channel potential) are degraded when the channel length is decreased, using conventional bulk materials such as silicon as the channel. Recently, two-dimensional semiconducting materials have emerged as promising candidates to replace silicon, as they can maintain excellent device electrostatics even at much reduced channel lengths. The second, more severe, challenge is that the supply voltage can no longer be scaled down by the same factor as the transistor dimensions because of the fundamental thermionic limitation of the steepness of turn-on characteristics, or subthreshold swing. To enable scaling to continue without a power penalty, a different transistor mechanism is required to obtain subthermionic subthreshold swing, such as band-to-band tunnelling. Here we demonstrate band-to-band tunnel field-effect transistors (tunnel-FETs), based on a two-dimensional semiconductor, that exhibit steep turn-on; subthreshold swing is a minimum of 3.9 millivolts per decade and an average of 31.1 millivolts per decade for four decades of drain current at room temperature. By using highly doped germanium as the source and atomically thin molybdenum disulfide as the channel, a vertical heterostructure is built with excellent electrostatics, a strain-free heterointerface, a low tunnelling barrier, and a large tunnelling area. Our atomically thin and layered semiconducting-channel tunnel-FET (ATLAS-TFET) is the only planar architecture tunnel-FET to achieve subthermionic subthreshold swing over four decades of drain current, as recommended in ref. 17, and is also the only tunnel-FET (in any architecture) to achieve this at a low power-supply voltage of 0.1 volts. Our device is at present the thinnest-channel subthermionic transistor, and has the potential to open up new avenues for ultra-dense and low-power integrated circuits, as well as for ultra-sensitive biosensors and gas sensors.
PubMed: 26432247
DOI: 10.1038/nature15387 -
Visual Neuroscience Jan 2017Rod-cone gap junctions mediate the so-called "secondary rod pathway", one of three routes that convey rod photoreceptor signals across the retina. Connexin 36 (Cx36) is...
Rod-cone gap junctions mediate the so-called "secondary rod pathway", one of three routes that convey rod photoreceptor signals across the retina. Connexin 36 (Cx36) is expressed at these gap junctions, but an unidentified connexin protein also seems to be expressed. Cx36 knockout mice have been used extensively in the quest to dissect the roles in vision of all three pathways, with the assumption, never directly tested, that rod-cone electrical coupling is abolished by deletion of this connexin isoform. We previously showed that when wild type mouse cones couple to rods, their apparent dynamic range is extended toward lower light intensities, with the appearance of large responses to dim flashes (up to several mV) originating in rods. Here we recorded from the cones of Cx36del[LacZ]/del[LacZ] mice and found that dim flashes of the same intensity evoked at most small sub-millivolt responses. Moreover, these residual responses originated in the cones themselves, since: (i) their spectral preference matched that of the recorded cone and not of rods, (ii) their time-to-peak was shorter than in coupled wild type cones, (iii) a pharmacological block of gap junctions did not reduce their amplitude. Taken together, our data show that rod signals are indeed absent in the cones of Cx36 knockout mice. This study is the first direct demonstration that Cx36 is crucial for the assembly of functional rod-cone gap junctional channels, implying that its genetic deletion is a reliable experimental approach to eliminate rod-cone coupling.
Topics: Animals; Connexins; Electrophysiology; Female; Gap Junctions; Light; Male; Membrane Potentials; Mice; Mice, Inbred C57BL; Mice, Knockout; Photic Stimulation; Retinal Cone Photoreceptor Cells; Retinal Rod Photoreceptor Cells; Gap Junction delta-2 Protein
PubMed: 28965521
DOI: 10.1017/S0952523817000037 -
Journal of Glaucoma Aug 2022Twenty-four-hour IOP measurements with a CLS showed that among IOP indicators studied, the range of IOP fluctuation was most important and significantly larger in NTG...
PRCIS
Twenty-four-hour IOP measurements with a CLS showed that among IOP indicators studied, the range of IOP fluctuation was most important and significantly larger in NTG eyes compared with nonglaucoma eyes.
PURPOSE
We conducted the present study to determine (1) the best factor for distinguishing normal tension glaucoma (NTG) and nonglaucoma subjects based on the intraocular pressure (IOP) values measured by a CLS and (2) the optimal cutoff values of that factor.
SUBJECTS AND METHODS
The eyes of 18 nonglaucoma subjects and 26 NTG patients were examined. We evaluated 5 indicators: maximum IOP value, SD, IOP fluctuation range, the cosine-fit curve amplitude, and the amplitude of dual-harmonic regression values. We determined the indicators' cutoff values to distinguish between nonglaucoma subjects and NTG patients with the area under the curve.
RESULTS
The mean IOP values were 12.3±2.7 mm Hg in the nonglaucoma eyes and 12.5±3.1 mm Hg in the NTG eyes ( P =0.824). All 5 indicators were significantly higher in the NTG group. The best factor to distinguish the nonglaucoma subjects and NTG patients was the IOP fluctuation range ( P <0.0001, area under the curve=0.844); the cutoff level value was 436.5 millivolt equivalents.
CONCLUSIONS
Twenty-four-hour IOP measurements with a CLS showed that among IOP indicators studied, the range of IOP fluctuation was most important and significantly larger in NTG eyes compared with nonglaucoma eyes.
Topics: Circadian Rhythm; Contact Lenses; Glaucoma, Open-Angle; Humans; Intraocular Pressure; Low Tension Glaucoma; Tonometry, Ocular
PubMed: 35766388
DOI: 10.1097/IJG.0000000000002071 -
Micromachines Apr 2018This paper proposes an electric power self-supply module for the wireless sensor network (WSN) sensor node. The module includes an electromagnetic vibration energy...
This paper proposes an electric power self-supply module for the wireless sensor network (WSN) sensor node. The module includes an electromagnetic vibration energy harvester based on micro-electro-mechanical system (MEMS) technology and a processing circuit. The vibration energy harvester presented in this paper is fabricated by an integrated microfabrication process and consists of four similar and relatively independent beam vibration elements. The main functions of the processing circuit are to convert the output of the harvester from unstable alternating current (AC) to stable direct current (DC), charge the super capacitor, and ensure the stable output of the super capacitor. The preliminary test results of the harvester chip show that the chip can output discontinuous pulse voltage, and the range of the voltage value is from tens to hundreds of millivolts in the vibration frequency range of 10⁻90 Hz. The maximum value that can be reached is 563 mV (at the vibration frequency of 18 Hz). The results of the test show that the harvester can output a relatively high voltage, which can meet the general electric power demand of a WSN sensor node.
PubMed: 30424095
DOI: 10.3390/mi9040161 -
IEEE Journal of Translational... 2019The electrocardiogram (ECG) plays an important role in the diagnosis of heart diseases. However, most patterns of diseases are based on old datasets and stepwise...
INTRODUCTION
The electrocardiogram (ECG) plays an important role in the diagnosis of heart diseases. However, most patterns of diseases are based on old datasets and stepwise algorithms that provide limited accuracy. Improving diagnostic accuracy of the ECG can be done by applying machine learning algorithms. This requires taking existing scanned or printed ECGs of old cohorts and transforming the ECG signal to the raw digital (time (milliseconds), voltage (millivolts)) form.
OBJECTIVES
We present a MATLAB-based tool and algorithm that converts a printed or scanned format of the ECG into a digitized ECG signal.
METHODS
30 ECG scanned curves are utilized in our study. An image processing method is first implemented for detecting the ECG regions of interest and extracting the ECG signals. It is followed by serial steps that digitize and validate the results.
RESULTS
The validation demonstrates very high correlation values of several standard ECG parameters: PR interval 0.984 +/-0.021 (p-value < 0.001), QRS interval 1+/- SD (p-value < 0.001), QT interval 0.981 +/- 0.023 p-value < 0.001, and RR interval 1 +/- 0.001 p-value < 0.001.
CONCLUSION
Digitized ECG signals from existing paper or scanned ECGs can be obtained with more than 95% of precision. This makes it possible to utilize historic ECG signals in machine learning algorithms to identify patterns of heart diseases and aid in the diagnostic and prognostic evaluation of patients with cardiovascular disease.
PubMed: 32166049
DOI: 10.1109/JTEHM.2019.2949784 -
Frontiers in Neuroscience 2018Fundamental structure and dynamics of spontaneous neuronal activities without apparent peripheral inputs were analyzed in the vagal complex (VC), whose activities had...
Fundamental structure and dynamics of spontaneous neuronal activities without apparent peripheral inputs were analyzed in the vagal complex (VC), whose activities had been generally thought to be produced almost passively to peripheral cues. The analysis included the caudal nucleus of the tractus solitarius-a main gateway for viscerosensory peripheral afferents and involved dynamically and critically in cardiorespiratory brainstem networks. In the present study, a possibility of self-organized brain activity was addressed in the VC. While VC neurons exhibited sparse firing in anesthetized rats and in preparations, we identified peculiar features of the emergent electrical population activity: (1) Spontaneous neuronal activity, in most cases, comprised both respiration and cardiac cycle components. (2) Population potentials of polyphasic high amplitudes reaching several millivolts emerged in synchrony with the inspiratory phase of respiratory cycles and exhibited several other characteristic temporal dynamics. (3) The spatiotemporal dynamics of local field potentials (LFPs), recorded simultaneously over multiple sites, were characterized by a stochastic emergence of high-amplitude synchrony. By adjusting amplitude and frequency (phase) over both space and time, the traveling synchrony exhibited varied degrees of coherence and power with a fluctuating balance between mutual oscillators of respiratory and cardiac frequency ranges. Full-fledged large-scale oscillatory synchrony over a wide region of the VC emerged after achieving a maximal stable balance between the two oscillators. Distinct somatic (respiratory; ~1 Hz) and visceral (autonomic; ~5 Hz) oscillators seemed to exist and communicate co-operatively in the brainstem network. Fluctuating oscillatory coupling may reflect varied degrees of synchrony influenced by the varied amplitude and frequency of neuronal activity in the VC. Intranuclear micro-, intrabulbar meso-, and wide-ranging macro-circuits involving the VC are likely to form nested networks and strategically interact to maintain a malleable whole-body homeostasis. These two brainstem oscillators could orchestrate neuronal activities of the VC, and other neuronal groups, through a phase-phase coupling mechanism to perform specific physiological functions.
PubMed: 30618595
DOI: 10.3389/fnins.2018.00978 -
Science (New York, N.Y.) Dec 2009Interconversion of water and hydrogen in unitized regenerative fuel cells is a promising energy storage framework for smoothing out the temporal fluctuations of solar...
Interconversion of water and hydrogen in unitized regenerative fuel cells is a promising energy storage framework for smoothing out the temporal fluctuations of solar and wind power. However, replacement of presently available platinum catalysts by lower-cost and more abundant materials is a requisite for this technology to become economically viable. Here, we show that the covalent attachment of a nickel bisdiphosphine-based mimic of the active site of hydrogenase enzymes onto multiwalled carbon nanotubes results in a high-surface area cathode material with high catalytic activity under the strongly acidic conditions required in proton exchange membrane technology. Hydrogen evolves from aqueous sulfuric acid solution with very low overvoltages (20 millivolts), and the catalyst exhibits exceptional stability (more than 100,000 turnovers). The same catalyst is also very efficient for hydrogen oxidation in this environment, exhibiting current densities similar to those observed for hydrogenase-based materials.
Topics: Biomimetic Materials; Catalysis; Catalytic Domain; Electrochemical Techniques; Electrodes; Hydrogen; Hydrogen-Ion Concentration; Hydrogenase; Ligands; Nanotubes, Carbon; Nickel; Oxidation-Reduction; Phosphines; Protons; Sulfuric Acids
PubMed: 19965754
DOI: 10.1126/science.1179773 -
Journal of the American Association For... Jan 2018Capuchin monkeys are a species of arboreal primate found in all South American countries. These monkeys have been highlighted for their potential for biomedical research...
Capuchin monkeys are a species of arboreal primate found in all South American countries. These monkeys have been highlighted for their potential for biomedical research due to their anatomic and physiologic similarities and genetic homology with humans. Here we characterized the electrocardiographic tracings from 12 healthy, young capuchin monkeys that were restrained with ketamine and midazolam. All 12 monkeys had normal sinus rhythms. Neither P-wave duration, PR interval, QT interval, nor P- or R-wave amplitude (in millivolts) differed between males and females. The P waves were small, monophasic, and positive in all animals. The QRS complex showed positive polarity in the D1, D2, aVL, aVF, V2, V4, and V10 derivations and negative polarity in the D3, aVR, and rV2 leads. The T wave exhibited a negative polarity only in the aVR derivation in all animals in the study, and no significant difference was present between sexes. The ST segment was isoelectric in both sexes and lacked reductions and elevations. The anesthetic protocol was well tolerated all of the monkeys and allowed for diagnostic-quality acquisition, measurement, and characterization of the electrocardiogram and establishment of the normal electrocardiographic parameters of chemically restrained capuchin monkeys.
Topics: Animals; Cebus; Electrocardiography; Female; Heart; Male; Reference Values; Species Specificity
PubMed: 29402346
DOI: No ID Found -
Nanotechnology Feb 2009Piezoresponse force microscopy was applied to directly study individual type I collagen fibrils with diameters of approximately 100 nm isolated from bovine Achilles...
Piezoresponse force microscopy was applied to directly study individual type I collagen fibrils with diameters of approximately 100 nm isolated from bovine Achilles tendon. It was revealed that single collagen fibrils behave predominantly as shear piezoelectric materials with a piezoelectric coefficient on the order of 1 pm V(-1), and have unipolar axial polarization throughout their entire length. It was estimated that, under reasonable shear load conditions, the fibrils were capable of generating an electric potential up to tens of millivolts. The result substantiates the nanoscale origin of piezoelectricity in bone and tendons, and implies also the potential importance of the shear load-transfer mechanism, which has been the principle basis of the nanoscale mechanics model of collagen, in mechanoelectric transduction in bone.
Topics: Achilles Tendon; Animals; Cattle; Collagen Type I; Elastic Modulus; Electromagnetic Fields; Macromolecular Substances; Materials Testing; Molecular Conformation; Nanostructures; Particle Size; Shear Strength; Surface Properties; Vibration
PubMed: 19417467
DOI: 10.1088/0957-4484/20/8/085706 -
Die Naturwissenschaften Jul 1999Paramecium generates persistent shifts of the membrane potential of a few millivolts depending on its orientation with respect to the gravity vector. The resulting...
Paramecium generates persistent shifts of the membrane potential of a few millivolts depending on its orientation with respect to the gravity vector. The resulting potential-induced modulation of the speed of propulsion is called gravikinesis because it acts to neutralize, fully or in part, sedimentation. Gravisensitivity is maximal at neutral orientation, i.e., in horizontally swimming cells, when the gravitational force per unit membrane area is at minimum. Stimulus-response relationships and energetic considerations show that sensing of the gravity vector by a nonspecialized, single-cell organism ranks among the most sensitive mechanoreceptors known in nature.
Topics: Animals; Calcium Channels; Gravitation; Gravity Sensing; Locomotion; Mechanoreceptors; Membrane Potentials; Motor Activity; Orientation; Paramecium; Potassium Channels; Swimming
PubMed: 11536922
DOI: 10.1007/s001140050634