Thermal Effects and Self-Heating Time Constant for GMR Recording Heads

2003 ◽  
Author(s):  
Lydia Baril ◽  
Erhard Schreck ◽  
Al Wallash
Keyword(s):  
Time Constant ◽  
Heating Time ◽  
Heat Sources ◽  
Resistance Change ◽  
Self Heating ◽  
Recording Heads ◽  
Gmr Sensors ◽  
Gmr Sensor ◽  
Short Time ◽  
Current Transients

An understanding of the temperature of the GMR reader element used in disk drives during operating and non-operating condition is critical to optimize its performance. Self-heating and/or external heat sources will cause an increase in the temperature of the GMR sensor. In this work we concentrate on the self-heating effect due to bias current. Experiments that monitored the resistance change during very short current pulses showed that state-of-the-art GMR sensors have an extremely short time-constant that is less than 2 ns. This work is applicable to the current transients that the GMR head experiences during electrical crosstalk, electrostatic discharge and thermal asperities.

Construction of a Magnetic Biosensor for Pathogen Detection

2008 ◽  
Vol 2 (2) ◽  
Author(s):  
Yuanpeng Li ◽  
Marlene Castro ◽  
Hyungsoon Im ◽  
Xiaofeng Yao ◽  
Sang-Hyun Oh ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
Giant Magnetoresistance ◽  
Pathogen Detection ◽  
Gold Surface ◽  
Thiol Group ◽  
Microfluidic System ◽  
Microfluidic Channels ◽  
Resistance Change ◽  
Gmr Sensors ◽  
Gmr Sensor

Current methods for pathogen detection require days before a result is available, while biosensors offer the advantage of quick, on the spot results. In this project we present the proof of concept of a biosensor that uses giant magnetoresistance (GMR) sensors and a microfluidic system. The bioprobe consists of a 30 bp oligonucleotide, 5′ functionalized with a thiol group (T-DNA30) immobilized on a gold surface. Hybridization was tested with a 5′-biotinylated oligonucleotide complementary to T-DNA30 to which Streptavidin-R-Phycoerythrin was attached later. The difference in fluorescence between the target sample and control samples was observed using a scanning laser confocal fluorescence microscope. The GMR device consists of an Ir0.8Mn0.2∕Co0.9Fe0.1∕Cu∕Co0.9Fe0.1∕Ni0.82Fe0.12 multilayer structure. Magnetic nanoparticles were deposited directly on the surface of the GMR sensors. An external magnetic field was employed to polarize the nanoparticles, which can then be detected by comparing the resistance change loops of the GMR sensors before and after their deposition. A transparent elastomer, polydimethylsiloxane (PDMS), was used for the microfluidic system. The system comprises two microfluidic channels separated by a 200μm PDMS wall. The channel width is 200μm and its height 100μm. The PDMS channel was permanently bonded to the SiO2 surface of the GMR sensor. The integrated biosensor will immobilize thiolated DNA on the gold surface below which the GMR device is located. For hybridization, biotinylated DNA will be used. Finally, magnetic nanoparticles, coated with streptavidin will be attached to the hybridized DNA and detected by the GMR device.

scholarly journals A tandem giant magnetoresistance assay for one-shot quantification of clinically relevant concentrations of N-terminal pro-B-type natriuretic peptide in human blood

2021 ◽  
Author(s):  
Fanda Meng ◽  
Weisong Huo ◽  
Jie Lian ◽  
Lei Zhang ◽  
Xizeng Shi ◽  
...  
Keyword(s):  
Detection Limit ◽  
Giant Magnetoresistance ◽  
Dynamic Range ◽  
Point Of Care ◽  
Sample Volume ◽  
Small Sample ◽  
Broad Dynamic Range ◽  
Gmr Sensors ◽  
Gmr Sensor ◽  
Sample Volume Requirement

AbstractWe report a microfluidic sandwich immunoassay constructed around a dual-giant magnetoresistance (GMR) sensor array to quantify the heart failure biomarker NT-proBNP in human plasma at the clinically relevant concentration levels between 15 pg/mL and 40 ng/mL. The broad dynamic range was achieved by differential coating of two identical GMR sensors operated in tandem, and combining two standard curves. The detection limit was determined as 5 pg/mL. The assay, involving 53 plasma samples from patients with different cardiovascular diseases, was validated against the Roche Cobas e411 analyzer. The salient features of this system are its wide concentration range, low detection limit, small sample volume requirement (50 μL), and the need for a short measurement time of 15 min, making it a prospective candidate for practical use in point of care analysis.

STUDY ON TIME-CONSTANT MODELS OF SnO2pH SENSOR

2009 ◽  
Vol 21 (06) ◽  
pp. 449-452
Author(s):  
Chi-Wei Chen ◽  
Jung-Chuan Chou ◽  
Tai-Ping Sun ◽  
Shen-Kan Hsiung
Keyword(s):  
Time Constant ◽  
Electrochemical Impedance ◽  
Ph Value ◽  
Ph Sensor ◽  
Membrane Resistance ◽  
Hysteresis Effect ◽  
Equivalent Model ◽  
Resistance Change ◽  
Ph Buffer ◽  
Function Relationship

The aim of this study was to discuss the hysteresis effect of SnO2 pH sensor based on separative extended gate field effect transistor (SEGFET). Based on the theorem of three time-constants model, hysteresis model is linked with drift effect. Function relationship of pH value and time constant is also derived from the drift effects with difference pH value. Besides, electrochemical impedance spectroscopy (EIS) is utilized to interpret the mechanism of hysteresis effect. Experiments of EIS are carried out in different pH buffer solutions. An equivalent model of sensing membrane is obtained by theorem of EIS. The experimental results indicate that the equivalent circuit elements, such as membrane capacitance and membrane resistance, change with pH. This phenomenon is compared with other literatures and discussed on hysteresis effect.

scholarly journals A sensory integration account for time perception

2020 ◽  
Author(s):  
Alessandro Toso ◽  
Arash Fassihi ◽  
Luciano Paz ◽  
Francesca Pulecchi ◽  
Mathew E. Diamond
Keyword(s):  
Time Perception ◽  
Time Constant ◽  
Sensory Integration ◽  
Neuronal Firing ◽  
Elapsed Time ◽  
Leaky Integrator ◽  
Long Time ◽  
Integrator Model ◽  
Short Time ◽  
Sense Of Touch

ABSTRACTThe connection between stimulus perception and time perception remains unknown. The present study combines human and rat psychophysics with sensory cortical neuronal firing to construct a computational model for the percept of elapsed time embedded within sense of touch. When subjects judged the duration of a vibration applied to the fingertip (human) or whiskers (rat), increasing stimulus mean speed led to increasing perceived duration. Symmetrically, increasing vibration duration led to increasing perceived intensity. We modeled spike trains from vibrissal somatosensory cortex as input to dual leaky integrators – an intensity integrator with short time constant and a duration integrator with long time constant – generating neurometric functions that replicated the actual psychophysical functions of rats. Returning to human psychophysics, we then confirmed specific predictions of the dual leaky integrator model. This study offers a framework, based on sensory coding and subsequent accumulation of sensory drive, to account for how a feeling of the passage of time accompanies the tactile sensory experience.

346. Measurements of the rate of change of temperature in high temperature-short time pasteurization plant

1947 ◽  
Vol 15 (1-2) ◽  
pp. 18-23
Author(s):  
F. Steghart
Keyword(s):  
High Temperature ◽  
Time Constant ◽  
Rate Of Change ◽  
Hot Water ◽  
Water Pipe ◽  
Temperature Changes ◽  
Rates Of Change ◽  
High Temperature Short Time ◽  
Short Time

It has recently been claimed that in modern high temperature-short time pasteurization plant fluctuations in temperature of the order of 1° F./sec. are unusual and probably artefacts, and that an instantaneous drop is certainly fictitious.It has, nevertheless, been shown that such rapid drops in temperature do in fact occur frequently in high temperature-short time plants of the type investigated. The plant investigated was not of the latest design incorporating devices for speeding up the control by injecting steam directly into the hot-water pipe.Temperature changes of the order of those in question were first observed by Mattick & Hiscox(1) of the National Institute for Research in Dairying, who carried out tests on pasteurization plant using a small mirror galvanometer with a very short time constant. The maximum rates of change were, however, not observed.

Ventilatory afterdischarge and central respiratory drive interactions in the awake goat

1994 ◽  
Vol 76 (1) ◽  
pp. 416-423 ◽  
Author(s):  
M. J. Engwall ◽  
C. A. Smith ◽  
J. A. Dempsey ◽  
G. E. Bisgard
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Time Constant ◽  
Minute Ventilation ◽  
Respiratory Drive ◽  
Arterial Pco2 ◽  
Expiratory Muscle ◽  
Series Of Experiments ◽  
Short Time ◽  
Animal Preparation

We have previously established the existence of ventilatory afterdischarge (VAD) in the awake goat by means of an isolated perfused carotid body (CB) technique. In the present series of experiments we used this animal preparation to examine the effects of systemic (central nervous system) hypoxia, mild hypercapnia, and hypocapnia on the manifestation of VAD in ventilatory variables and respiratory muscle electromyogram activity after hypoxic stimulation of the isolated CB. With systemic isocapnic normoxia, inspired minute ventilation remains above control for 30–40 s (time constant = 16.8 s) after termination of CB hypoxia; however, with systemic hypocapnia, VAD is short (time constant = 5.5 s) and hypoventilation is common after removal of CB stimulation. During mild systemic hypercapnia, VAD is prolonged (time constant = 39.9 s). However, systemic (central nervous system) hypoxia did not decrease VAD (time constant = 17.0 s). These results indicate that the manifestation of VAD is more sensitive to the level of arterial PCO2 and central chemoreceptor activity than it is to the state of central oxygenation. Inspiratory and expiratory muscle electromyogram activities qualitatively tracked ventilation during CB stimulation and during the VAD period in all conditions.

Inhibition of Afferent Transmission in the Feeding Circuitry of Aplysia: Persistence Can Be as Important as Size

2005 ◽  
Vol 93 (5) ◽  
pp. 2940-2949 ◽  
Author(s):  
Colin G. Evans ◽  
Adarli Romero ◽  
Elizabeth C. Cropper
Keyword(s):  
Time Constant ◽  
Synaptic Input ◽  
Low Frequencies ◽  
Lateral Process ◽  
Postsynaptic Potentials ◽  
Inhibitory Postsynaptic Potentials ◽  
Functional Inhibition ◽  
Long Time ◽  
Spike Initiation ◽  
Short Time

We are studying afferent transmission from a mechanoafferent, B21, to a follower, B8. During motor programs, afferent transmission is regulated so that it does not always occur. Afferent transmission is eliminated when spike propagation in B21 fails, i.e., when spike initiation is inhibited in one output region-B21's lateral process. Spike initiation in the lateral process is inhibited by the B52 and B4/5 cells. Individual B52 and B4/5-induced inhibitory postsynaptic potentials (IPSPs) in B21 differ. For example, the peak amplitude of a B4/5-induced IPSP is four times the amplitude of a B52 IPSP. Nevertheless, when interneurons fire in bursts at physiological (i.e., low) frequencies, afferent transmission is most effectively reduced by B52. Although individual B52-induced IPSPs are small, they have a long time constant and summate at low firing frequencies. Once IPSPs summate, they effectively block afferent transmission. In contrast, individual B4/5-induced IPSPs have a relatively short time constant and do not summate at low frequencies. B52 and B4/5 therefore differ in that once synaptic input from B52 becomes effective, afferent transmission is continuously inhibited. In contrast, periods of B4/5-induced inhibition are interspersed with relatively long intervals in which inhibition does not occur. Consequently, the probability that afferent transmission will be inhibited is low. In conclusion, it is widely recognized that afferent transmission can be regulated by synaptic input. Our experiments are, however, unusual in that they relate specific characteristics of postsynaptic potentials to functional inhibition. In particular we demonstrate the potential importance of the IPSP time constant.

Disc Mechanics With Trans-Endplate Partial Nucleotomy are not Fully Restored Following Cyclic Compressive Loading and Unloaded Recovery

2006 ◽  
Vol 128 (6) ◽  
pp. 823-829 ◽  
Author(s):  
Edward J. Vresilovic ◽  
Wade Johannessen ◽  
Dawn M. Elliott
Keyword(s):  
Cyclic Loading ◽  
Stress Relaxation ◽  
Nucleus Pulposus ◽  
Time Constant ◽  
Annulus Fibrosus ◽  
Compressive Loading ◽  
Magnetic Resonance Images ◽  
Mechanical Behaviors ◽  
Short Time

Mechanical function of the intervertebral disc is maintained through the interaction between the hydrated nucleus pulposus, the surrounding annulus fibrosus, and the superior and inferior endplates. In disc degeneration the normal transfer of load between disc substructures is compromised. The objective of this study was to explore the mechanical role of the nucleus pulposus in support of axial compressive loads over time. This was achieved by measuring the elastic slow ramp and viscoelastic stress-relaxation mechanical behaviors of cadaveric sheep motion segments before and after partial nucleotomy through the endplate (keeping the annulus fibrosus intact). Mechanics were evaluated at five conditions: Intact, intact after 10,000cycles of compression, acutely after nucleotomy, following nucleotomy and 10,000cycles of compression, and following unloaded recovery. Radiographs and magnetic resonance images were obtained to examine structure. Only the short time constant of the stress relaxation was altered due to nucleotomy. In contrast, cyclic loading resulted in significant and large changes to both the stiffness and stress relaxation behaviors. Moreover, the nucleotomy had little to no effect on the disc mechanics after cyclic loading, as there were no significant differences comparing mechanics after cyclic loading with or without the nucleotomy. Following unloaded recovery the mechanical changes that had occurred as a consequence of cyclic loading were restored, leaving only a sustained change in the short time constant due to the trans-endplate nucleotomy. Thus the swelling and redistribution of the remaining nucleus pulposus was not able to fully restore mechanical behaviors. This study reveals insights into the role of the nucleus pulposus in disc function, and provides new information toward the potential role of altered nucleus pulpous function in the degenerative cascade.

Restrictions on the short time constant astrophysics

1972 ◽  
Vol 19 (2) ◽  
pp. 431-439 ◽  
Author(s):  
G. Cavallo ◽  
A. Ventura
Keyword(s):  
Time Constant ◽  
Short Time
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