Impact-Initiation Sensitivity of High-Temperature PTFE-Al-W Reactive Materials

Drop-weight tests were conducted to investigate the impact-initiation sensitivity of high-temperature PTFE-Al-W reactive materials. The test results show that the impact-initiation sensitivity of the materials more than doubles with increasing the sample temperature from 25 to 350 °C. Combined with the impact-induced initiation process recorded by high-speed video and the difference between reacted and unreacted residues, the crack-induced initiation mechanism was revealed. The rapid propagation of crack provides a high-temperature and aerobic environment where Al reacts violently to PTFE, which induces the initiation. Moreover, the influence of sample temperature on the sensitivity was discussed and analyzed. The analysis results indicate that the sensitivity shows a temperature interval effect, and 127 and 327 °C are the interval boundaries where the sensitivity changes significantly. The sensitivity may leaps at 127 °C and increases more rapidly in the temperature interval from 127 to 327 °C, but hardly changes after the temperature reaches 327 °C.

A novel principle to localize the sensitivity of waveform tomography using wave interferences at the observation boundary

When using waveform tomography to perform high-resolution imaging of a medium, it is vital to calculate the sensitivity in order to describe how well a model fits a given set of data and how the sensitivity changes with the spatial distribution of the heterogeneities. The traditional principle behind calculating the sensitivity—for detecting small changes—suffers from an inherent limitation in case other structures, not of interest, are present along the wave propagation path. We propose a novel principle that leads to enhanced localization of the sensitivity of the waveform tomography, without having to know the intermediate structures. This new principle emerges from a boundary integral representation which utilizes wave interferences observed at multiple points. When tested on geophysical acoustic wave data, this new principle leads to much better sensitivity localization and detection of small changes in seismic velocities, which were otherwise impossible. Overcoming the insensitivity to a target area, it offers new possibilities for imaging and monitoring small changes in properties, which is critical in a wide range of disciplines and scales.

The Site Tilt and Lander Transfer Function from the Short-Period Seismometer of InSight on Mars

ABSTRACT The National Aeronautics and Space Administration InSight mission has deployed the seismic experiment, SEIS, on the surface of Mars, and has recorded a variety of signals including marsquakes and dust devils. This work presents results on the tilt and local noise sources, which provide context to aid interpretation of the observed signals and allow an examination of the near-surface properties. Our analysis uses data recorded by the short-period sensors on the deck, throughout deployment and in the final configuration. We use thermal decorrelation to provide an estimate of the sol-to-sol tilt. This tilt is examined across deployment and over a Martian year. After each modification to the site, the tilt is seen to stabilize over 3–20 sols depending on the action, and the total change in tilt is <0.035°. Long-term tilt over a Martian year is limited to <0.007°. We also investigate the attenuation of lander-induced vibrations between the lander and SEIS. Robotic arm motions provide a known lander source in the 5–9 Hz bandwidth, yielding an amplitude attenuation of lander signals between 100 and 1000 times. The attenuation of wind sensitivity from the deck to ground presents a similar value in the 1.5–9 Hz range, thus favoring a noise dominated by lander vibrations induced by the wind. Wind sensitivities outside this bandwidth exhibit different sensitivity changes, indicating a change in the coupling. The results are interpreted through a finite-element analysis of the regolith with a depth-dependent Young’s modulus. We argue that discrepancies between this model and the observations are due to local compaction beneath the lander legs and/or anelasticity. An estimate for the effective Young’s modulus is obtained as 62–81 MPa, corroborating previous estimates for the top layer duricrust.

Visuo-Acoustic Stimulation’s Role in Synaptic Plasticity: A Review of the Literature

Brain plasticity is the capacity of cerebral neurons to change, structurally and functionally, in response to experiences. This is an essential property underlying the maturation of sensory functions, learning and memory processes, and brain repair in response to the occurrence of diseases and trauma. In this field, the visual system emerges as a paradigmatic research model, both for basic research studies and for translational investigations. The auditory system remains capable of reorganizing itself in response to different auditory stimulations or sensory organ modification. Acoustic biofeedback training can be an effective way to train patients with the central scotoma, who have poor fixation stability and poor visual acuity, in order to bring fixation on an eccentrical and healthy area of the retina: a pseudofovea. This review article is focused on the cellular and molecular mechanisms underlying retinal sensitivity changes and visual and auditory system plasticity.

Highly Sensitive Quartz-Based Sensing System for the Detection of Subpercentage Changes in the Relative Permittivity of Liquids Flowing in Microchannels

We describe a highly sensitive quartz sensor for measuring changes in the relative permittivity of liquids flowing in microchannels. The proposed method uses a highly stable oscillator and capacitance-dependent quartz crystal together with a capacitance-sensitive element attached along the microchannel. A change in the relative permittivity of the fluid induces a change in the capacitance of the sensitive element in the aF range, which is detected as a change in the resonant frequency. The advantages of the proposed measurement technique are the extreme sensitivity (changes in the relative permittivity as low as 0.01% can be detected), the temperature independence of the setup between 10 and 40 °C, the stability (the frequency reading fluctuates within 0.025 Hz), and the low cost compared with the methods that use impedance analyzers or lock-in amplifiers. We present the use of the method to detect changes in mixtures of liquids if the temperature, volume fractions, or properties of one liquid change. The method presents a useful tool for applications in biology, chemistry, pharmacy, and technology in general wherever accurate monitoring of compositions of fluids is required and where changes, for example, due to temperature variation or mixture aging, need to be detected in real time.

A longitudinal study of the antilipolytic effect of insulin in women following bariatric surgery

Insulin resistance of glucose utilization is fully restored following BMI normalization after bariatric surgery. We investigated if this also pertains to insulin-induced effects on fatty acid handling. Forty-three women with obesity (OB) were investigated before and 2 years after Roux-en-Y gastric by-pass when BMI was <30 kg/m2 (PO) and compared with 26 never obese women (NO). The Adipo-IR index was used as measure of insulin antilipolytic sensitivity. Changes (delta) in circulating glycerol and fatty acid levels during hyperinsulinemic euglycemic clamp represented the insulin maximum antilipolytic effect. Overall fatty acid utilization was reflected by delta fatty acids minus 3 × delta glycerol. Adipo-IR was higher in OB than in NO and PO (p < 0.0001), the latter two groups having similar values. Insulin lowered glycerol levels by about 70% in all groups, but delta glycerol was 30% larger in PO than in NO (p = 0.04). Delta adds and adds utilization were similar in all groups. We conclude that women with obesity, whose BMI is normalized after bariatric surgery, have improved maximum in vivo antilipolytic effect of insulin above expected in absolute but not relative terms as regards glycerol changes, while the handling of circulating fatty acids is changed to the normal state.

Rate and Temperature Effect in Nanoindentation Testing on Hardness in SLM IN718

The microstructure and mechanical hardness of Inconel 718 (INC718) hexagonal honeycomb cellular structure manufactured by Selective Laser Melting (SLM) was studied in this work. Non-heat-treated SLM-produced samples with cell wall thicknesses of 0.4, 0.6 and 0.8 mm were studied. The hardness was measured using MTS Nanoindenter. For room temperature, continuous hardness measurements over penetration depths up to 2 µm under three different strain rates of 0.02, 0.05 and 0.08 s−1 was performed. For the 100 and 200°C, single hardness measurements at eight different depths were performed. The grain size was found to change considerably as the cell wall thickness changed from 0.6 mm to 0.4 mm compared to the change from 0.8 mm to 0.6 mm. similar trend in mechanical hardness reduction and strain rate sensitivity changes were observed between the three samples. The microstructure and hardness showed anisotropy between the planes parallel and perpendicular to the build planes as well. Temperature and strain rate indentation size effect model developed by the second author was modified and used to evaluate the intrinsic material length scale used in gradient plasticity theory.

Simulation of FDSOI-ISFET with Tunable Sensitivity by Temperature and Dual-Gate Structure

This work investigates the different sensitivities of an ion-sensitive field-effect transistor (ISFET) based on fully depleted silicon-on-insulator (FDSOI). Using computer-aided design (TCAD) tools, the sensitivity of a single-gate FDSOI based ISFET (FDSOI-ISFET) at different temperatures and the effects of the planar dual-gate structure on the sensitivity are determined. It is found that the sensitivity increases linearly with increasing temperature, reaching 890 mV/pH at 75 °C. By using a dual-gate structure and adjusting the control gate voltage, the sensitivity can be reduced from 750 mV/pH at 0 V control gate voltage to 540 mV/pH at 1 V control gate voltage. The above sensitivity changes are produced because the Nernst limit changes with temperature or the electric field generated by different control gate voltages causes changes in the carrier movement. It is proved that a single FDSOI-ISFET can have adjustable sensitivity by adjusting the operating temperature or the control gate voltage of the dual-gate device.

Diagnostic properties of sensitivity changes in patients with maxillofacial fractures

Aim: Verify the accuracy of objective assessments compared to subjective tests in detecting changes in somatosensory perception in individuals affected by maxillofacial trauma. Methods: The review (PROSPERO n ° CRD42019125546) used the databases: MEDLINE, Cochrane, EMBASE, LILACS and other bibliographic resources. Prospective and retrospective studies that used objective and subjective methods of assessing facial sensitivity in maxillofacial fractures were included. There was no restriction on language or publication date. Risk of bias was assessed using the QUADAS-2. Data extraction and analysis were performed using a form developed for the study. Results: 21 studies were included. The clinical objective examination mainly includes assessments of: tactile sensitivity (95.24%) and nociceptive sensitivity (57.14%). The subjective assessment was based on the patient’s report, spontaneously (61.90%), guided by structured questionnaires (33.33%) and/or using scales (9.52%) to measure the degree of impairment. In risk of bias assessment, were observed no adequate interpretation and classification of changes in subjective sensitivity, subject to inappropriate analysis of the data. In addition, the studies bring several instruments without standardization for assessing sensory modalities. Conclusion: The objective assessment is a complement to the subjective assessment, using the touch assessment as the main parameter in the profile of the facial peripheral integrity, associated or not with nociceptive assessment. Lack of consensus on the indication of specific instruments for testing is a limiting factor. Thus, based on the studies, is proposed a minimum battery of sensitivity assessment to obtain an overview of the patient’s peripheral nervous situation.