Direct Sensor Research Articles

Directional Sensors for Recording Uterine EMG During Pregnancy.

Multichannel uterine electromyography (uEMG) during pregnancy is traditionally performed with electrocardiography (ECG) sensors. Similar signals are often observed in two or more channels, suggesting the ECG sensors report activities originating from the same location on the uterus. To improve signal source localization, we designed a directional sensor or "Area Sensor". Here we compare Area Sensors with ECG sensors for source localization. Subjects were ≥ 38 wks experiencing regular contractions. 6 Area Sensors (n = 8) or 6 to 7 ECG sensors (n = 7) were used to record multichannel uEMG for 60min. For each sensor type, the similarity of signals observed in pairs of channels during contractions was assessed by quantifying channel crosstalk. Since crosstalk depends on the separation between sensors, analyses were performed within distance groups: A 9-12cm; B 13-16cm; C 17-20cm; D 21-24cm; E ≥ 25cm. For ECG sensors, crosstalk was 67.9 ± 14.4% in group A, decreasing to 27.8 ± 17.5% in group E. For Area Sensors, crosstalk was 24.6 ± 18.6% in Group A, decreasing to 12.5 ± 13.8% in group E. Area Sensors showed less crosstalk than ECG sensors in distance groups A, B, C and D, with all p < 0.002. Compared with ECG sensors, Area Sensors are more directional and report uterine activity from a smaller area of the uterine wall. Using 6 Area Sensors separated by at least 17cm provides acceptably independent multichannel recording. This introduces the possibility of non-invasively evaluating uterine synchronization and the strength of individual uterine contractions in real time.

Stable directional amplification in one-dimensional non-Hermitian single-band systems

We investigate the directional amplification of non-Hermitian single-band systems in one dimension by using two models. The first model is the Hatano-Nelson model with added cavity decay and the second model is a linear lattice with fully asymmetric next-nearest-neighbor hopping. Based on the Dyson equation, we calculate the Green's functions of the two models analytically and investigate the directional amplification of a weak probe field. We find that, although the periodic-boundary spectrum of the two models determines the frequency interval in which the probe field can be directionally amplified, the open-boundary spectrum influences not only the bandwidth of the amplification curve but also the shape of the transmission curves. The bandwidth and the gain can be tuned independently by the parameters of the system. We also find that, for lattices with finite size, the frequency interval of the directional amplification shrinks due to the finite-size effects. Our thorough analysis is expected to provide a deeper insight into the directional amplification in non-Hermitian single-band systems and a tool for designing directional amplifiers and sensors.

Alleviation of thermal nociception depends on heat-sensitive neurons and a TRP channel in the brain

Acute avoidance of dangerous temperatures is critical for animals to prevent or minimize injury. Therefore, surface receptors have evolved to endow neurons with the capacity to detect noxious heat so that animals can initiate escape behaviors. Animals including humans have evolved intrinsic pain-suppressing systems to attenuate nociception under some circumstances. Here, using Drosophila melanogaster, we uncovered a new mechanism through which thermal nociception is suppressed. We identified a single descending neuron in each brain hemisphere, which is the center for suppression of thermal nociception. These Epi neurons, for Epione-the goddess of soothing of pain-express a nociception-suppressing neuropeptide Allatostatin C (AstC), which is related to a mammalian anti-nociceptive peptide, somatostatin. Epi neurons are direct sensors for noxious heat, and when activated they release AstC, which diminishes nociception. We found that Epi neurons also express the heat-activated TRP channel, Painless (Pain), and thermal activation of Epi neurons and the subsequent suppression of thermal nociception depend on Pain. Thus, while TRP channels are well known to sense noxious temperatures to promote avoidance behavior, this work reveals the first role for a TRP channel for detecting noxious temperatures for the purpose of suppressing rather than enhancing nociception behavior in response to hot thermal stimuli.

Sleep-wakeup scheduling algorithm for lifespan maximization of directional sensor networks: a discrete cuckoo search optimization algorithm

Directional sensor networks (DSNs) are ad-hoc networks which are utilized in different industrial applications. Their usual engagements are to monitor and to perform the coverage of all specific targets in the observing fields permanently. These kinds of networks include numerous configurable directional sensors in which they can be utilized in one of the possible directions along with the one of their adjustable ranges. Although the energy harvesting methodology is being applied for these battery-hungry applications, the battery management and network lifetime maximization are still prominent challenges. In this paper, the network lifetime extension is formulated to a discrete optimization problem which is a famous non-deterministic polynomial time hardness (NP-Hard) problem. To solve this combinatorial problem, a discrete cuckoo search algorithm (D-CSA) is designed and is called in several rounds. A cover is a sub set of configured sensors capable of monitoring all targets in the observing field. In each round, the most efficient cover is constituted along with its activation time. In the determined activation time, the sensors in the cover are scheduled in wakeup mode whereas others are set in sleep mode to save energy. Despite other meta-heuristic algorithms, this proposed algorithm utilizes the novel defined discrete walking around procedures that makes to reach a good balance between exploration and exploitation in this complex search space. The proposed algorithm has been tested in different scenarios to be evaluated. The simulation results in the variety circumstances prove the superiority of the proposed algorithm is about 20.29%, 19.55%, 14.40%, 14.51%, 7.70% and 8.03% in term of average lifespan improvement against H-MNLAR, Hm-LifMax-BC, GA, ACOSC, H-GATS, and HDPSO algorithms, respectively. The results also show the high potential scalability of the proposed algorithm.

Performance-based optimal sensor placement method for single-layer reticulated shells considering modal observability and damage identifiability

Structural health monitoring allows for the early detection of structural damage and provide valuable insight into structural performance. However, duo to numerous degrees of freedom and dense vibration modals, designing a sensor placement scheme for Single-Layer Reticulated Shells (SLRSs) is a challenging task. This paper introduces two performance indexes, namely the modal observability and damage identifiability, to quantitatively evaluate the efficiency of the sensor system. Subsequently, based on these indexes, the multi-objective optimization algorithm, as well as the performance-based design concepts, a novel performance-based optimal sensor placement (OSP) method for SLRSs is proposed. Two types of sensor placement performance curves, namely the sensor placement effect curve and the sensor placement proportion curve, are presented to determine the optimal number and placement of sensors in different directions. Numerical examples demonstrate that the proposed method can generate OSP schemes that meet various performance targets, and the performance-based OSP method is superior to the simple multi-objective OSP method. Furthermore, suggestion on selecting the total number of sensors for practical engineering applications is also provided.

Safety, usability, and performance of a wireless left atrial pressure monitoring system in patients with heart failure: the VECTOR-HF trial.

In heart failure (HF), implantable hemodynamic monitoring devices have been shown to optimize therapy, anticipating clinical decompensation and preventing hospitalization. Direct left-sided hemodynamic sensors offer theoretical benefits beyond pulmonary artery pressure (PAP) monitoring systems. We evaluated the safety, usability, and performance of a novel left atrial pressure (LAP) monitoring system in HF patients. The VECTOR-HF study(NCT03775161) was a first-in-human, prospective, multicenter, single-arm, clinical trial enrolling 30 patients with HF. The device consisted of an interatrial positioned leadless sensor, able to transmit LAP data wirelessly. After three months, a right heart catheterization (RHC) was performed to correlate mean pulmonary capillary wedge pressure (PCWP) with simultaneous mean LAP obtained from the device. Remote LAP measurements were then used to guide patient management. The miniaturized device was successfully implanted in all 30 patients, without acute Major Adverse Cardiac and Neurological Events (MACNE). At 3 months, freedom from short-term MACNE was 97%. Agreement between sensor-calculated LAP and PCWP was consistent, with a mean difference of -0.22±4.92mmHg, the correlation coefficient and the Lin's Concordance Correlation Coefficient values were equal to 0.79 (P<0.0001) and 0.776 (95%CI=0.582-0.886), respectively. Preliminary experience with VLAP-based HF management was associated with significant improvements in NYHA functional class (32% of patients reached NYHA II class at 6 months, P<0.005; 60% of patients at 12 months, P<0.005) and 6-minute walk-test distance (from 244.59±119.59m at baseline to 311.78±129.88m after 6 months, P<0.05, and 343.95±146.15m after 12 months, P<0.05). The V-LAP™ monitoring system proved to be generally safe and provided a good correlation with invasive PCWP. Initial evidence also suggests possible improvement in HF clinical symptoms. This article is protected by copyright. All rights reserved.

101 Environmental conditions in equine indoor arenas: A descriptive study

Indoor arenas serve a unique purpose at equine facilities, yet there has been minimal research conducted examining the internal environment within them. Survey data identified dust, moisture, temperature, and air movement as concerns of indoor arena users and one-time characterizations of 37 facilities within 100 miles of Lexington, KY demonstrated air movement below the still air threshold (100 ft/min (0.51 m/s)) for livestock facilities in 87% of the indoor arenas. To better understand the environment within indoor arenas, 15 facilities selected from the 37 facilities noted above were monitored for 1 week during both the winter and summer seasons between October 2020 and February 2022. Temperature, relative humidity, dew point, solar radiation, and air speed data were collected every 5 min using the HOBO RX3000 Remote Monitoring Station with the HOBOnet Temperature/Relative Humidity Sensor, HOBOnet Solar Radiation Sensor, and HOBOnet Ultrasonic Wind Speed and Direction Sensor. All measurements displayed a distinct diurnal pattern with clear trends for the different seasons of data collection. Conducting paired t-tests between the climate control and non-climate-controlled facilities demonstrated statistically significant differences for the winter temperature (P = 0.006), winter and summer relative humidity (P < 0.001 andP < 0.001), and winter and summer dew point temperatures (P < 0.001 and P < 0.001). Temperature, relative humidity, and dew point temperatures were higher in the climate-controlled arenas likely due to the presence of heating mechanisms and insulation. Similar to the indoor arena characterization data, the air speeds observed during the environmental monitoring for all of the indoor arenas were below the threshold for still air in livestock facilities (100 ft/min (0.51 m/s)). Solar radiation for both seasons peaked around 3 p.m., but the differences were statistically significant (P < 0.001) with a summer day experiencing an average of 10.77 Watts per square meter, compared with 6.46 Watts per square meter during the winter. This is consistent with changes in the position and intensity of the sun throughout the year though the opening of windows and doors may also impact the amount of sunlight entering the facilities. Sensor technology and implementation provides a better understanding of the interior environment and how indoor arena design can impact and improve these conditions.

Bitewing radiography dosimetry of the PORTRAY stationary-intraoral tomosynthesis imaging system

This study measured effective (E) and equivalent doses from adult and child 3-dimensional (3D) and 2D posterior bitewing (PBW) examinations using the PORTRAY stationary-intraoral tomosynthesis radiography system. Adult and child phantoms and optically stimulated luminescent dosimeters were used to measure doses for adult-4 and child-2 projection PBW examinations acquired without (W/O) and with (W) a direct digital sensor in the beam path. Child doses without and with thyroid shielding were measured. Three-dimensional examination E values (μSv) W/O and W were 16.7 and 7.3 for adult, 9.2 and 3.5 for child, and 8.7 and 3.0 with thyroid shielding, respectively. Two-dimensional examination E values W/O and W were 4.3 and 1.5 for adult, 2.1 and 0.6 for child, and 2.0 and 0.5 with shielding, respectively. Sensor presence reduced E for all adult and child examinations (P=.0001). Child E was reduced compared with adult E for both sensor conditions in 3D (P < .0001) and 2D (P ≤ .0043) imaging. Adult and child 3D W/O and W equivalent thyroid doses did not differ (P ≥ .9996). However, child 2D W/O and W doses were lower (P ≤ .0002). Shielding produced no reduction (P ≥ .1128) for either 3D condition or 2D with the sensor (P=.6615) but reduced child 2D dose without the sensor. Inclusion of a sensor yielded significant reductions in adult and child E. Sensor presence impacted thyroid dose reduction more than shielding.

Bile acid conditioned Dendritic cells through FXR and specialize T cell function in the ileum

Abstract The accumulation of locally-reabsorbed bile acids (BAs) is suggested to contribute to the development of terminal ileitis. Our previous data showed nuclear receptor Constitutive Androstane Receptor (CAR) can directs T cell adaptation to BAs in the ileum by promoting the IL-10 producing Tr1 cells to prevent ileitis. Still, the mechanisms by which BA activate CAR in ileal T cells is not known. As CAR is not recognized as a BA sensor, its activation in ileal T cells may involves indirect pathways, such as dendritic cells (DCs). Farnesoid X receptor (FXR), a direct primary BA sensor, is highly expressed in both human and mouse DCs. Therefore, we hypothesized that BA-sensing by mucosal DCs through FXR may condition mucosal T cells in the ileum to upregulate CAR and to enforce anti-inflammatory T cell functions. Our result indicated WT DCs exposed to direct FXR agonist, chenodeoxycholic acid (CDCA), displayed increased production of IL-23a and decreased IL-6. While, CD4 +T cells cocultured with CDCA-treated DCs displayed increased CAR/Nr1i3, and its targets, cMyc and MDR1. Importantly, these observations were diminished in DCs from FXR −/−mice. In addition, when FXR is depleted in DC (CD11cCreFXR fl/fl, FXR ΔDC), the DC migration in the intestine is deficient, with low expressions of CCL19, CCR9 and less CD11c +CD11b −CD103 +MHCII +migratory DC population in the mesenteric lymph nodes. Meanwhile, the FXR ΔDCmice failed to promote CAR/Nr1i3as well as IL10in T cells. Furthermore, FXR −/−RAG2 −/−mice developed severe ileitis after engrafted with WT naïve T cell. These results suggest that FXR specializes intestinal DC and T cell function in the ileum. Collectively, these studies will shed new light on the understanding and treatment of ileitis in patients.

Improved algorithms in directional wireless sensor networks

Improved algorithms in directional wireless sensor networks

Influence of applied bias on direct conversion X-ray sensing capability of nanocrystalline Ca9Ag(PO4)6(OH)2

Silver (Ag) doping in hydroxyapatite (HAP) can enhance the attenuation coefficient (μ) 0.65 cm2/g at photon energy 70 keV as compared with pure hydroxyapatite (μ = 0.31 cm2/g). In this study, direct conversion X-ray sensors were fabricated using pure HAP (Ca10(PO4)6(OH)2) and Ag-doped HAP (Ca9Ag(PO4)6(OH)2) to realize superior X-ray sensing capability. Thick films of wet-chemical route derived nanocrystalline samples were deposited on interdigitated electrodes by glass rod sliding technique and its X-ray instigated photocurrent characteristics at 2 V biased condition were recorded for different low doses (mGy). The observed sensitivity at 7.97 mGy dose reveals ten folds enhancement from 0.19 nC/mGy cm3 to 1.00 nC/mGy cm3. According to the “Grain boundary double Schottky potential barrier height model”, the formation of potential barrier height (φb) at the interface of grain and grain boundaries of nanocrystalline samples is identical to the Schottky barrier. By increasing the applied bias, the conduction band starts to bend and suppresses the potential barrier height (φb). In higher biased conditions, φb does not exist. Hence, the influence of applied bias on direct conversion X-ray sensing capability of Ca9Ag(PO4)6(OH)2 was investigated and discussed in detail.

A Directional Chitosan Sound Sensor Based on Piezoelectric-Triboelectric Sensing.

Herein, we have constructed a directional sound sensor based on an anisotropic chitosan aerogel. Because of the lamellar porous structure, this chitosan aerogel exhibits a distinct anisotropic behavior, featuring the compressive stress along the direction of the parallel laminate structure, being approximately 2.6 times that in the orthogonal direction. Simultaneously, the chitosan aerogel is used as a directional sound-sensing material, which exhibits excellent acoustic-electric conversion performance with a marked difference in the direction perpendicular to the laminate structure than in the parallel direction. The CSANG has an optimum electrical output of 66 V and 9.2 μA under a sound stimulation of 150 Hz and 120 dB in the orthogonal direction of the laminate structure. Therefore, this directional chitosan sound sensor with excellent biocompatibility and sound sensitivity demonstrates promising application potential in the field of intelligent sensing and artificial cochlea.

Probabilistic coverage in mobile directional sensor networks: a game theoretical approach

Probabilistic coverage in mobile directional sensor networks: a game theoretical approach

Enhanced low-dose x-ray sensing nature of nanocrystalline CaWO4 sensor

Extensive research on the development of superior sensitive X-ray sensors by many researchers is due to their increased demand in numerous fields, like medical radiography, security inspection, and scientific research areas. Especially in healthcare, repeated or long-term high-dose X-ray exposure on patients may cause serious health hazards. Therefore, developing a superior sensing low dose X-ray sensor is essential. In this present work, a nanocrystalline CaWO4 thick film above an interdigitated electrode was developed as a direct conversion X-ray sensor that operates at different low doses (mGy) using an intraoral pulsed X-ray (70 keV) machine. The X-ray instigated photocurrent of nano-CaWO4 thick film was examined under different applied bias to obtain superior sensitivity of the device. The nano-CaWO4 thick film exhibit sensitivity of 10 nC/mGycm3 at 0.20 mGy (0.06 s) low dose under 5 V applied bias. A suitable mechanism was proposed to explain the nano-CaWO4 thick film sensing behaviour at different biased conditions.

A low-power DTOF image sensor with double-frame-multiplexing mode for long-range detection

A novel time-to-digital converter (TDC) operation mode, called double-frame-multiplexing (DFM), is proposed for time-of-flight (TOF) measurements. It is based on the separate detection of the minimum distance and depth of the measured targets, which reduces the power consumption of in-pixel TDCs and expands the maximum detection distance under high resolution. A 64 × 64 direct TOF image sensor chip is fabricated in a 0.18 μm CMOS process. Driven by a 125 MHz multi-phase clock and a 50 MHz data readout clock, the chip achieves a maximum frame rate of 20 kframe/s, a maximum detection distance of 750 m (5 μs), and a maximum depth of field of 3 m (20 ns) with a temporal resolution of 1 ns. The DFM mode reduces the average power consumption to 60 mW without consideration of SPADs. The worst-case measured differential nonlinearity is −0.61/+0.69 least significant bit (LSB) and the maximum integral nonlinearity is −1.06/+0.66 LSB.

Fascicle dynamics of the tibialis anterior muscle reflect whole-body walking economy

Humans can inherently adapt their gait pattern in a way that minimizes the metabolic cost of transport, or walking economy, within a few steps, which is faster than any known direct physiological sensor of metabolic energy. Instead, walking economy may be indirectly sensed through mechanoreceptors that correlate with the metabolic cost per step to make such gait adaptations. We tested whether velocity feedback from tibialis anterior (TA) muscle fascicles during the early stance phase of walking could potentially act to indirectly sense walking economy. As participants walked within a range of steady-state speeds and step frequencies, we observed that TA fascicles lengthen on almost every step. Moreover, the average peak fascicle velocity experienced during lengthening reflected the metabolic cost of transport of the given walking condition. We observed that the peak TA muscle activation occurred earlier than could be explained by a short latency reflex response. The activation of the TA muscle just prior to heel strike may serve as a prediction of the magnitude of the ground collision and the associated energy exchange. In this scenario, any unexpected length change experienced by the TA fascicle would serve as an error signal to the nervous system and provide additional information about energy lost per step. Our work helps provide a biomechanical framework to understand the possible neural mechanisms underlying the rapid optimization of walking economy.

Plastic Classification Using Optical Parameter Features Measured with the TMF8801 Direct Time-of-Flight Depth Sensor.

We demonstrate a methodology for non-contact classification of five different plastic types using an inexpensive direct time-of-flight (ToF) sensor, the AMS TMF8801, designed for consumer electronics. The direct ToF sensor measures the time for a brief pulse of light to return from the material with the intensity change and spatial and temporal spread of the returned light conveying information on the optical properties of the material. We use measured ToF histogram data of all five plastics, captured at a range of sensor to material distances, to train a classifier that achieves 96% accuracy on a test dataset. To extend the generality and provide insight into the classification process, we fit the ToF histogram data to a physics-based model that differentiates between surface scattering and subsurface scattering. Three optical parameters of the ratio of direct to subsurface intensity, the object distance, and the time constant of the subsurface exponential decay are used as features for a classifier that achieves 88% accuracy. Additional measurements at a fixed distance of 22.5 cm showed perfect classification and revealed that Poisson noise is not the most significant source of variation when measurements are taken over a range of object distances. In total, this work proposes optical parameters for material classification that are robust over object distance and measurable by miniature direct time-of-flight sensors designed for installation in smartphones.

Development and Evaluation of a Locally Designed Solar Integrated Egg Incubator

There is need for subsistence poultry farmers to maximize chick production to supply the increasing demand for poultry meat. This research developed and evaluated an egg incubator powered by a renewable energy source generated from solar modules. The incubator was incorporated with temperature and humidity sensors which measured and regulated the conditions suitable for the egg incubation. The direct current (DC) heater, sensor, microcontroller and DC fan provided suitable temperature and humidity for the eggs. The developed incubator was evaluated by monitoring the temperature and Relative Humidity (RH) readings over a range of time and the hatchability rate was also evaluated. The temperature within the incubator chamber ranged 37-38°C with an error margin of +0.1oC while the RH ranged between of 30-35% with an error margin of +5%. An average hatchability rate of 92% was obtained from the evaluation of the incubator. The evaluation gave a standardized temperature and relative humidity range of values necessary for incubation of eggs. The study has shown that solar energy could be used to successfully power incubator systems with good hatchability for the whole incubation period.

Muscle stem cells get a new look: Dynamic cellular projections as sensors of the stem cell niche.

Cellular mechanisms whereby quiescent stem cells sense tissue injury and transition to an activated state are largely unknown. Quiescent skeletal muscle stem cells (MuSCs, also called satellite cells) have elaborate, heterogeneous projections that rapidly retract in response to muscle injury. They may therefore act as direct sensors of their niche environment. Retraction is driven by a Rac-to-Rho GTPase activity switch that promotes downstream MuSC activation events. These and other observations lead to several hypotheses: (1) projections are morphologically dynamic at quiescence, providing a surveillance function for muscle damage; (2) quiescent projection dynamics are regulated by the relative balance of Rac and Rho activities promoted by niche-derived cues; (3) projections, particularly their associated filopodia, sense tissue damage via changes to the biomechanical properties of the niche and/or detection of signaling cues released by damaged myofibers; and (4) the dynamic nature of projections results in a population of MuSCs with heterogeneous functional properties. These concepts may extend to other types of quiescent stem cells, as well as prove useful in translational research settings.

Directional Torsion Sensor Based on a Two-Core Fiber with a Helical Structure

A fiber-optic torsion sensor based on a helical two-core fiber (HTCF) is proposed and experimentally demonstrated for simultaneously measuring torsion angle and torsion direction. The sensor consists of a segment of HTCF and two single-mode fibers (SMFs) forming a Mach-Zehnder interferometer (MZI). The helical structure is implemented by pre-twisting a 1 cm long two-core fiber (TCF). The performance of the sensor with pre-twisted angles of 180°, 360°, and 540° is experimentally analyzed. The results show that the sensor can realize the angular measurement and effectively distinguish the torsion direction. It is worth noting that the sensor has maximum sensitivity when the pre-twist angle is 180 degrees. The obtained wavelength sensitivities of torsion and temperature are 0.242 nm/(rad/m) and 32 pm/°C, respectively. The sensor has the advantages of easy fabrication, low cost, compact structure, and high sensitivity, which is expected to yield potential applications in fields where both torsion angle and direction measurements are required.