Recently, the safety and reliability of unmanned aerial vehicles (UAVs) have gained increasing interest, and data-driven anomaly detection methods have been widely studied. However, it is still challenging to build an accurate and reliable detector due to the scarcity of labeled data and complex spatial-temporal characteristics of flight data with noises and disturbances. To this end, this article proposes an autoencoder-based unsupervised anomaly detection framework with multivariate flight data without labeled information. Specifically, we designed a new robust spatial-temporal autoencoder (RSTAE) model based on the temporal convolution network (TCN), the convolution neural network (CNN), and the attention mechanism to extract the complicated spatial-temporal correlations in multivariate flight data. Instead of using the traditional mean square error (mse) loss function, a modified loss function based on maximum correntropy criteria (MCC) is introduced to enhance the robustness of our RSTAE model during its training process. To further improve the anomaly detection performance, a dynamic threshold strategy is used. Experimental results on real flight data demonstrate the superior performance of the proposed method compared with several autoencoder-based methods in terms of six evaluation metrics.

This study investigated the relationships of systemic low-frequency oscillations (sLFOs) measured at different peripheral sites in resting state, during passive leg raising (PLR), and during a paced breathing (PB) test. Twenty-five healthy subjects (21 to 57 years old; males: 13 and females: 12) were recruited for these experiments. During the experiments, the fluctuations of oxyhemoglobin concentration were measured at six peripheral sites (left and right toes, fingertips, and earlobes) using a multichannel near-infrared spectroscopy instrument developed by our group. We applied cross-correlation and frequency component analyses on the data. The results showed that the sLFO signals in the symmetric peripheral sites were highly correlated, with time delays close to zero, whereas the correlation coefficients decreased between the sLFO signals of asymmetric sites, with delays up to several seconds. Furthermore, in PLR/PB tests, we found that PB caused wider and more robust changes in hemoglobin concentrations at peripheral sites compared to PLR. Among six peripheral sites, earlobes were the most sensitive to these perturbations, followed by fingertips, and then toes. Lastly, we showed that the perturbation signals may have different coupling mechanisms than the sLFO signals. The study deepened our understanding of the sLFO signals and establishes baseline measures for developing perfusion biomarkers to assess peripheral vascular integrity.

Functional near-infrared spectroscopy (fNIRS) is an imaging technique that noninvasively measures the product of cerebral hemodynamics (concentration changes of oxygenated and deoxygenated hemoglobin; $\mathrm{\Delta }{C}_{{\mathrm{O}}_2\mathrm{Hb}}$ and $\mathrm{\Delta }{C}_{\mathrm{HHb}}$) and optical path length ($L$), using light in the near-infrared spectrum (650 to 900 nm).¹ 2. ^{– 3} Because hemodynamic changes are related to local neuronal activity through neurovascular coupling,^4,5 fNIRS is commonly used to interpret brain activity and function. fNIRS has been widely used in research, clinical, and educational purposes⁶ due to its cost-effectiveness, safety, flexibility, higher spatial resolution than electroencephalography, and better temporal resolution than functional magnetic resonance imaging (fMRI).⁷ fNIRS systems are more compact than fMRI, which enables practical and continuous bedside monitoring even in infants and young children.⁸ 9. ^{– 10} fNIRS provides better motion tolerance; therefore, fNIRS is suitable for examining the challenging patients with restless symptoms^11,12 and subjects actively engaging in movement such as walking and running.^13,14 Furthermore, cochlear implant patients can safely undergo fNIRS measurement because there is no magnetic field that may endanger patients.^15,16

Terahertz waves lie within the rotation and oscillation energy levels of biomolecules, and can directly couple with biomolecules to excite nonlinear resonance effects, thus causing conformational or configuration changes in biomolecules. Based on this mechanism, we investigated the effect pattern of 0.138 THz radiation on the dynamic growth of neurons and synaptic transmission efficiency, while explaining the phenomenon at a more microscopic level. We found that cumulative 0.138 THz radiation not only did not cause neuronal death, but that it promoted the dynamic growth of neuronal cytosol and protrusions. Additionally, there was a cumulative effect of terahertz radiation on the promotion of neuronal growth. Furthermore, in electrophysiological terms, 0.138 THz waves improved synaptic transmission efficiency in the hippocampal CA1 region, and this was a slow and continuous process. This is consistent with the morphological results. This phenomenon can continue for more than 10 min after terahertz radiation ends, and these phenomena were associated with an increase in dendritic spine density. In summary, our study shows that 0.138 THz waves can modulate dynamic neuronal growth and synaptic transmission. Therefore, 0.138 terahertz waves may become a novel neuromodulation technique for modulating neuron structure and function.

Introduction: Terahertz waves lie within the energy range of hydrogen bonding and van der Waals forces. They can couple directly with proteins to excite non-linear resonance effects in proteins, and thus affect the structure of neurons. However, it remains unclear which terahertz radiation protocols modulate the structure of neurons. Furthermore, guidelines and methods for selecting terahertz radiation parameters are lacking.Methods: In this study, the propagation and thermal effects of 0.3–3 THz wave interactions with neurons were modelled, and the field strength and temperature variations were used as evaluation criteria. On this basis, we experimentally investigated the effects of cumulative radiation from terahertz waves on neuron structure. Results: The results show that the frequency and power of terahertz waves are the main factors influencing field strength and temperature in neurons, and that there is a positive correlation between them. Appropriate reductions in radiation power can mitigate the rise in temperature in the neurons, and can also be used in the form of pulsed waves, limiting the duration of a single radiation to the millisecond level. Short bursts of cumulative radiation can also be used. Broadband trace terahertz (0.1–2 THz, maximum radiated power 100 μW) with short duration cumulative radiation (3 min/day, 3 days) does not cause neuronal death. This radiation protocol can also promote the growth of neuronal cytosomes and protrusions.Discussion: This paper provides guidelines and methods for terahertz radiation parameter selection in the study of terahertz neurobiological effects. Additionally, it verifies that the short-duration cumulative radiation can modulate the structure of neurons.

Transcranial ultrasound stimulation (TUS) has shown promising prospects as a non-invasive neuromodulation technique for both animals and humans. However, ultrasonic propagation characteristics within the brain differ significantly from those in free space. There is currently a lack of comprehensive studies on the effects of skull thickness on focal point position, full width at half maximum (FWHM), and acoustic intensity. This study investigates the transcranial acoustic field characteristics of 500 kHz focused ultrasound, with a focus on the impact of skull thickness. The study combined finite element simulations to evaluate the effects of skull thickness on 500 kHz focused ultrasound with experimental investigations across multiple species (mouse, rat, pig, and human). The simulation and experimental results indicate that the skull changes focal length ( -4.4 ∼ 4.7 mm) and axial focal region ( -7.93 ∼ 7.59 mm), and the skull causes significant attenuation of acoustic intensity, which increases with skull thickness. The attenuation rate of human skulls is greater than 80%. We found that the skull thickness has little effect on focal point position (< 0.9 mm) and focal region (< 1.44 mm) in lateral and vertical directions. Skull thickness has great influence on focal length, axial focal region and acoustic intensity, but has little effect on focal point position and focal region in lateral and vertical directions. And improving axial spatial resolution is a potential method to reduce changes of axial focal region.