Two Realizations of the Wearable PPG Sensor Working in Reflectance Mode for Measurement in Weak Magnetic Field

The paper describes and compares properties of two realizations of wearable sensors based on the photoplethysmography (PPG) principle for non-invasive acquisition of the human heart rate. The designed sensors enable measurement of the PPG signal in the magnetic field environment with the inherent radiofrequency and electromagnetic disturbance. They can monitor the stress of a tested person during examination in the scanning area of the open-air magnetic resonance tomograph. The performed auxiliary experiments verify the practical functionality of both developed sensors including real-time wireless transmission of the measured PPG signal samples to the control device for further analysis and processing.

Multimodal and Multiview Wound Monitoring with Mobile Devices

Along with geometric and color indicators, thermography is another valuable source of information for wound monitoring. The interaction of geometry with thermography can provide predictive indicators of wound evolution; however, existing processes are focused on the use of high-cost devices with a static configuration, which restricts the scanning of large surfaces. In this study, we propose the use of commercial devices, such as mobile devices and portable thermography, to integrate information from different wavelengths onto the surface of a 3D model. A handheld acquisition is proposed in which color images are used to create a 3D model by using Structure from Motion (SfM), and thermography is incorporated into the 3D surface through a pose estimation refinement based on optimizing the temperature correlation between multiple views. Thermal and color 3D models were successfully created for six patients with multiple views from a low-cost commercial device. The results show the successful application of the proposed methodology where thermal mapping on 3D models is not limited in the scanning area and can provide consistent information between multiple thermal camera views. Further work will focus on studying the quantitative metrics obtained by the multi-view 3D models created with the proposed methodology.

Large-Area and Ultrathin MEMS Mirror Using Silicon Micro Rim

A large-area and ultrathin MEMS (microelectromechanical system) mirror can provide efficient light-coupling, a large scanning area, and high energy efficiency for actuation. However, the ultrathin mirror is significantly vulnerable to diverse film deformation due to residual thin film stresses, so that high flatness of the mirror is hardly achieved. Here, we report a MEMS mirror of large-area and ultrathin membrane with high flatness by using the silicon rim microstructure (SRM). The ultrathin MEMS mirror with SRM (SRM-mirror) consists of aluminum (Al) deposited silicon nitride membrane, bimorph actuator, and the SRM. The SRM is simply fabricated underneath the silicon nitride membrane, and thus effectively inhibits the tensile stress relaxation of the membrane. As a result, the membrane has high flatness of 10.6 m−1 film curvature at minimum without any deformation. The electrothermal actuation of the SRM-mirror shows large tilting angles from 15° to −45° depending on the applied DC voltage of 0~4 VDC, preserving high flatness of the tilting membrane. This stable and statically actuated SRM-mirror spurs diverse micro-optic applications such as optical sensing, beam alignment, or optical switching.

COMPARISON OF VARIOUS 18F-FDG PET/CT ACQUISITION PROTOCOLS IN CHILDREN WITH HODGKIN’S LYMPHOMA

In adults with oncological diseases, most PET/CT studies with 18F-FDG are performed using a scanning protocol with a reduced scanning area (r-PET/CT). In pediatric oncology, PET/CT with 18F-FDG is recommended to be performed in the «whole body» mode. We hypothesized that the use of r-PET/CT in children with Hodgkin's lymphoma (HL) may be sufficient without loss of diagnostic value. Materials and methods of research: a comparative analysis of PET/CT scanning protocols in «whole body» mode and r-PET/CT mode in children with HL was carried out. The retrospective analysis included 105 patients aged 0–18 years. All patient underwent primary whole-body PET/CT examinations at the time of initial staging and intermediate follow-up PET/CT scan after 2-cycle of chemotherapy. 210 PET/CT studies were retrospectively analyzed. Results: in 94 (89,5%) of 105 patients the identified lesions were localized within the area of the field-of-view of r-PET/CT, and additional lesions detected in 11 (10,5%) patients in the whole-body PET/CT examinations have not affected the results of staging and management. Conclusion: the detection of additional foci of pathological metabolic activity beyond r-PET/CT has no further impact on the stage of the disease, the protocol of treatment and the evaluation of the early response to the therapy. The advantage of r-PET/CT protocol is the reduction in radiation exposure and study time, which is very important for pediatric patients with HL.

Intelligent selection of scanning area for ICP based pose estimation of space structures

Future autonomous satellite repair missions would benefit from higher accuracy pose estimates of target satellites. Constraint analysis provides a sensitivity index which can be used as a registration accuracy predictor. It was shown that point cloud configurations with higher values of this index returned more accurate pose estimates than unstable configurations with lower index values. Registration tests were conducted on four satellite geometries using synthetic range data. These results elucidate a means of determining the optimal scanning area of a given satellite for registration with the Iterative Closest Point (ICP) algorithm to return a highly accurate pose estimate.

Intelligent selection of scanning area for ICP based pose estimation of space structures

Future autonomous satellite repair missions would benefit from higher accuracy pose estimates of target satellites. Constraint analysis provides a sensitivity index which can be used as a registration accuracy predictor. It was shown that point cloud configurations with higher values of this index returned more accurate pose estimates than unstable configurations with lower index values. Registration tests were conducted on four satellite geometries using synthetic range data. These results elucidate a means of determining the optimal scanning area of a given satellite for registration with the Iterative Closest Point (ICP) algorithm to return a highly accurate pose estimate.

OCT angiography metrics predict intradialytic hypotension episodes in chronic hemodialysis patients: a pilot, prospective study

In chronic hemodialysis (HD) patients, intradialytic hypotension (IDH) is a complication that increases mortality risk. We run a pilot study to analyzing possible relationships between optical coherence tomography angiography (OCT-A) metrics and IDH with the aim of evaluating if OCT-A could represent a useful tool to stratify the hypotensive risk in dialysis patients. A total of 35 eyes (35 patients) were analyzed. OCT-A was performed before and after a single dialysis session. We performed OCT-A 3 × 3 mm and 6 × 6 mm scanning area focused on the fovea centralis. Patients were then followed up to 30 days (10 HD sessions) and a total of 73 IDHs were recorded, with 12 patients (60%) experiencing at least one IDH. Different OCT-A parameters were reduced after dialysis: central choroid thickness (CCT), 6 × 6 mm foveal whole vessel density (VD) of superficial capillary plexus (SPC) and 6 × 6 mm foveal VD of deep capillary plexus (DCP). At logistic regression analysis, IDH was positively associated with baseline foveal VD of SCP and DCP, while an inverse association was found with the choroid. In Kaplan–Meier analyses of patients categorized according to the ROC-derived optimal thresholds, CCT, the 3 × 3 foveal VD of SCP, the 3 × 3 mm and 6 × 6 mm foveal VD of DCP and the 6 × 6 mm foveal VD of SCP were strongly associated with a higher risk of IDH over the 30-days follow-up. In HD patients, a single OCT-A measurement may represent a non-invasive, rapid tool to evaluate the compliance of vascular bed to HD stress and to stratify the risk of IDH in the short term.

Broadband wide-angle active phased L-band antenna array emitters

The purpose of this article is to review and justify the choice of emitters for constructing energy-efficient high-performance broadband active phased L-band antenna array with wide-angle scanning in 2 planes. Phased antenna array characteristics, accepted as reference: wide scan angle in the H-plane  not less than ± 450; a wide range of frequencies  at least 40%; small overall dimensions of the radiating aperture, not allowing to consider the canvas without taking into account edge effects; high energy potential, which means high electric strength (up to 1 kW per channel); reduced spurious emission outside the scanning area (more than 45 °). Here are the requirements for the emitters of the above-described active phased antenna array: Emitters dimensions must comply with the structural requirements for the antenna array construction (array step, emitters arrangement method) and not «obscure» each other in the area of the working scanning angles in the E and H plane. Emitters spatial bottom width in the grating should not be less than the angular width of the area of electronic scanning of the active phased antenna array beam. Beam main lobe distortion in the scanning area by an amount higher than 1 dB is not allowed. The emitter in the grating should be consistent with the power system in the working range of scanning angles and frequencies. Reduced spurious emission in directions outside the scanning area. High efficiency, to ensure both reception and transmission, and sufficient dielectric strength with limited dimensions. As active phased antenna array emitters, the simplest weakly directional antennas are used, which is associated with their low cost and high manufacturability. Technical solutions in the class of vibrator antennas (dipoles) are subjected to further analysis. The use of dipole antenna arrays in wide-angle and broadband applications leads to a number of technical limitations, such as: limited broadband emitters (including and as part of the antenna array), determined by their design features and mutual influence; a limited sector of the formation of unidirectional radiation (shape stability (radiation pattern) in the frequency band, determined by the condition for the appearance of interference lobes and the mutual influence of the emitters, leading to distortion of the amplitude-phase distribution; the occurrence of the effect of «blinding» of the lattice in individual sectors of the scan and frequencies associated with the effects of external (spatial) and internal interaction of emitters. Based on the above requirements for emitters, taking into account the design features of the AFAR, the following most important technical problems can be identified, the solution of which must be considered: ensuring a wide working frequency band; ensuring consistency in a wide sector of scanning angles; ensuring a stable spatial pattern of the emitter in the grating. Consider the general constructive methods that can be used to solve the above problems. Group them according to the constituent structural elements of the vibrator: Shoulders shape of the vibrators. The main limitation of the classical symmetric vibrator emitter using is its small working frequency band (up to 10%). So the passband ( 2f ) of a symmetric half-wave vibrator can be estimated by the following expression [5, p. 187]: 4 73,1 2 f f0 ,  WВ where is WВ  the wave impedance of the vibrator. It is determined by the cross section, shape and length of the shoulders. Balancing device type. Using a coaxial line determines the presence of balancing devices to power the shoulders of the vibrators. In the decimeter range, various types of balancing devices are used, the basis of which are various loops (including the U-elbow), glasses, transformers and slots, as well as their combinations. 3. Reflector shape (including matching structural elements). In fixed sector vibrator headlamps, a solid conductive surface is usually used as a reflector. Its shape and location relative to the shoulders has a strong effect on the bottom of the emitter in the grating and the matching of the grating in wide scanning angles and in the frequency range. The factor taking into account the influence of a flat aperiodic reflector on the DN is estimated by the expression: Fра  sin(kdr cos ) , where is dr  the distance from the vibrator to the reflector.

Photo-response of Two-Dimensional Ruddlesden-Popper Perovskite Films for Photovoltaics

Two-dimensional (2D) Ruddlesden-Popper (RP) perovskites have emerged as a prospective candidate to address the instability issues of traditional perovskite solar cells. However, the mechanisms of charge carrier transport of 2D perovskite films obtained by the solution process still remain elusive. In this work, we proposed a novel characterization technique based on the Kelvin probe force microscopy (KPFM) to investigate the micro-scale morphology and surface potential (SP) of the BA2MA3Pb4I13 films. In additionally, a Xenon laser source was adopted to realize the in-situ scanning of the light response of the perovskite film. The obvious increase in surface potential values in the same scanning area before and after white light illumination indicated the emergence of photo-generated charge carriers. Based on the unique photophysical properties and form formation features of the hot-cast BA2MA3Pb4I13 films, we fabricated the 2D perovskite solar cells (PSCs) with an efficiency of 10.95%. As a result, the in-situ KPFM is capable to serve as an effective approach to investigating the charge carrier behaviors in the 2D perovskites for photovoltaic applications.