Long-Term Stability and Reproducibility of Magnetic Colloids Are Key Issues for Steady Values of Specific Power Absorption over Time

Main factors affecting the long-term stability of microwave oscillator frequency are discussed in this paper. External factors affect the signal frequency at the output of any actual source, causing it to continuously change over time. Long-term frequency instability could be attributed to aging of the material. So, it is necessary to take special environmental factors into account, when designing microwave oscillators for space electronic equipment.

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Long-Term Stability of Nickel in Resonant Micro-Mechanical Devices

MRS Proceedings ◽

10.1557/proc-308-147 ◽

1993 ◽

Vol 308 ◽

Cited By ~ 3

Author(s):

G.L. Povirk ◽

J. Bernstein ◽

S.B. Brown

Keyword(s):

Resonant Frequency ◽

Natural Frequency ◽

Structural Rearrangement ◽

Damage Initiation ◽

Term Stability ◽

Long Term Stability ◽

Micromechanical Device ◽

Mechanical Devices ◽

Over Time

ABSTRACTA nickel micromechanical device was resonated and the natural frequency of the structure was monitored over time. Any structural rearrangement or damage initiation in the material was expected to cause a corresponding change in the resonant frequency of the device. The resonant frequency of the device was initially about 31.8 kHz and the frequency was found to decline over time at a rate of 0.17 Hz/s.

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The Role of Electrode-Site Placement in the Long-Term Stability of Intracortical Microstimulation

Frontiers in Neuroscience ◽

10.3389/fnins.2021.712578 ◽

2021 ◽

Vol 15 ◽

Author(s):

Ramya L. Saldanha ◽

Morgan E. Urdaneta ◽

Kevin J. Otto

Keyword(s):

Active Sites ◽

Electrode Site ◽

Intracortical Microstimulation ◽

Term Stability ◽

Long Term Stability ◽

Custom Made ◽

Intracortical Electrodes ◽

Term Performance ◽

Over Time

Intracortical microelectrodes are neuroprosthetic devices used in brain-machine interfaces to both record and stimulate neural activity in the brain. These technologies have been improved by advances in microfabrication, which have led to the creation of subcellular and high-density microelectrodes. The greater number of independent stimulation channels in these devices allows for improved neuromodulation selectivity, compared to single-site microelectrodes. Elements of electrode design such as electrode-site placement can influence the long-term performance of neuroprostheses. Previous studies have shown that electrode-sites placed on the edge of a planar microelectrode have greater chronic recording functionality than sites placed in the center. However, the effect of electrode-site placement on long-term intracortical microstimulation (ICMS) is still unknown. Here, we show that, in rats chronically implanted with custom-made planar silicon microelectrodes, electrode-sites on the tip of the device outperformed those on both the edge and center in terms of the effect per charge delivered, though there is still a slight advantage to using edge sites over center sites for ICMS. Longitudinal analysis of ICMS detection thresholds over a 16-week period revealed that while all sites followed a similar trend over time, the tip and edge sites consistently elicited the behavioral response with less charge compared to center sites. Furthermore, we quantified channel activity over time and found that edge sites remained more active than center sites over time, though the rate of decay of active sites for center and edge sites was comparable. Our results demonstrate that electrode-site placement plays an important role in the long-term stability of intracortical microstimulation and could be a potential factor to consider in the design of future intracortical electrodes.

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Long-Term Stability of Cortisol Production and Metabolism Throughout Adolescence: Longitudinal Twin Study

Twin Research and Human Genetics ◽

10.1017/thg.2020.6 ◽

2020 ◽

Vol 23 (1) ◽

pp. 33-38 ◽

Cited By ~ 1

Author(s):

Britt J. van Keulen ◽

Conor V. Dolan ◽

Ruth Andrew ◽

Brian R. Walker ◽

Hilleke E. Hulshoff Pol ◽

...

Keyword(s):

Hpa Axis ◽

Excretion Rate ◽

Term Stability ◽

Long Term Stability ◽

Cortisol Metabolism ◽

The Stability ◽

Longitudinal Twin Study ◽

Hpa Axis Activity ◽

Over Time

AbstractLife-course experiences have been postulated to program hypothalamus–pituitary–adrenal (HPA) axis activity, suggesting that HPA axis activity is, at least partially, stable over time. Yet, there is paucity of data on the long-term stability of cortisol production and metabolism. We performed a prospective follow-up study in twins recruited from a nationwide register to estimate the stability of cortisol production and metabolism over time, and the contribution of genetic and environmental factors to this stability. In total, 218 healthy mono- and dizygotic twins were included. At the ages of 9, 12 and 17 years, morning urine samples were collected for assessment (by gas chromatography-tandem mass spectrometry) of cortisol metabolites, enabling the calculation of cortisol metabolite excretion rate and cortisol metabolism activity. Our results showed a low stability for both cortisol metabolite excretion rate (with correlations <.20) and cortisol metabolism activity indices (with correlations of .25 to .46 between 9 and 12 years, −.02 to .15 between 12 and 17 years and .09 to .28 between 9 and 17 years). Because of the low stability over time, genetic and environmental contributions to this stability were difficult to assess, although it seemed to be mostly determined by genetic factors. The low stability in both cortisol production and metabolism between ages 9 and 17 years reflects the dynamic nature of the HPA axis.

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Minimizing Oxidation of Freeze-Dried Monoclonal Antibodies in Polymeric Vials Using a Smart Packaging Approach

Pharmaceutics ◽

10.3390/pharmaceutics13101695 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1695

Author(s):

Nicole Härdter ◽

Tim Menzen ◽

Gerhard Winter

Keyword(s):

Monoclonal Antibodies ◽

Gas Permeability ◽

Drug Product ◽

Mechanical Shock ◽

Smart Packaging ◽

Term Stability ◽

Long Term Stability ◽

Freeze Dried ◽

Over Time

Primary containers made of cyclic olefin polymer (COP) have recently gained attention since they may overcome several risks and shortcomings of glass containers as they exhibit a high break resistance, biocompatibility, and homogeneous heat transfer during lyophilization. On the downside, COP is more permeable for gases, which can lead to an ingress of oxygen into the container over time. Since oxidation is an important degradation pathway for monoclonal antibodies (mAbs), the continuous migration of oxygen into drug product containers should be avoided overall. To date, no long-term stability studies regarding lyophilizates in polymer vials have been published, potentially because of the unbearable gas permeability. In this study, we demonstrate that after lyophilization in COP vials and storage of these vials in aluminum pouches together with combined oxygen and moisture absorbers (“smart packaging”), oxidation of two lyophilized therapeutic antibodies was as low as in glass vials due to the deoxygenated environment in the pouch. Nevertheless, active removal of oxygen from the primary container below the initial level over time during storage in such “smart” secondary packaging was not achieved. Furthermore, residual moisture was controlled. Overall, the smart packaging reveals a promising approach for long-term stability of biopharmaceuticals; in addition to COP’s known benefits, stable, low oxygen and moisture levels as well as the protection from light and cushioning against mechanical shock by the secondary packaging preserve the sensitive products very well.

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