Search Results (100)

Silicon Photomultipliers (SiPMs) are optical sensors widely used in space applications due to their high photon detection efficiency, low power consumption, and robustness. However, in Low Earth Orbit (LEO), their performance degrades over time due to prolonged exposure to ionizing radiation, primarily from trapped protons and electrons. The dominant radiation-induced effect in SiPMs is an increase in dark current, which can compromise detector sensitivity. This study investigates the potential of thermal annealing as a mitigation strategy for radiation damage in SiPMs. We designed and tested PCB-integrated heaters to selectively heat irradiated SiPMs and induce recovery processes. A PID-controlled system was developed to stabilize the temperature at 100 °C, and a remotely controlled experimental setup was implemented to operate under irradiation conditions. Two SiPMs were simultaneously irradiated with 9 MeV protons at the EDRA facility, reaching a 1 MeV neutron equivalent cumulative fluence of (9.5 ± 0.2) × 10⁸ cm⁻². One sensor underwent thermal annealing between irradiation cycles, while the other served as a control. Throughout the experiment, dark current was continuously monitored using a source measure unit, and I–V curves were recorded before and after irradiation. A recovery of more than 39% was achieved after only 5 min of thermal cycling at 100 °C, supporting this recovery approach as a low-complexity strategy to mitigate radiation-induced damage in space-based SiPM applications and increase device lifetime in harsh environments. Full article

Bioaerosol particles contribute to the reduced indoor air quality and cause various health issues, thus their concentration must be managed. Air cleaning is one of the most viable technological options for reducing quantities of indoor air contaminants. This study assesses the effectiveness of a prototype multi-stage air cleaner in reducing bioaerosol particle viability and concentrations. The single-pass type unit consisted of non-thermal plasma (NTP), ultraviolet-C (UV-C) irradiation, bipolar ionization (BI), and electrostatic precipitation (ESP) stages. The device was tested under controlled laboratory conditions using Escherichia coli (Gram-negative) and Lactobacillus casei (Gram-positive) bacteria aerosol at varying airflow rates (50–600 m³/h). The device achieved over 99% inactivation efficiency for both bacterial strains at the lowest airflow rate (50 m³/h). Efficiency declined with increasing airflow rates but remained above 94% at the highest flow rate (600 m³/h). Among the individual stages, NTP demonstrated the highest standalone inactivation efficiency, followed by UV-C and BI. The ESP stage effectively captured inactivated bioaerosol particles, preventing re-emission, while an integrated ozone decomposition unit maintained ozone concentrations below safety thresholds. These findings show the potential of multi-stage air cleaning technology for reducing bioaerosol contamination in indoor environments, with applications in healthcare, public spaces, and residential settings. Full article

The root walls of immature permanent teeth are often weak, thin, and short, making regenerative endodontic treatment (RET) necessary. The goal of RET is to create a favorable environment for further root development. A biomimetic approach is essential for thorough disinfection, followed by the preservation and potential stimulation of stem cells from surrounding tissue to enable root regeneration and continued development. The objective of this study was to assess temperature changes on the external root surface, structural alterations in the internal root walls following irradiation with a 940 nm diode laser, and the biocompatibility of stem cells from the apical papilla (SCAPs). Irradiation was performed with varying output powers (0.5 W, 1 W, 1.5 W, and 2 W) in continuous mode for 5 s over four consecutive cycles. Thermographic measurements during irradiation, the micro-CT analysis of root samples, and mitochondrial activity of SCAPs were evaluated. The heating effect correlated directly with a higher output power and thinner root walls. A 1 W output power was found to be safe for immature teeth, particularly in the apical third of the root, while 1.5 W could be safely used for mature mandibular incisors. Diode laser irradiation at 1 W and 1.5 W significantly stimulated SCAPs’ mitochondrial activity within 24 h post-irradiation, indicating a potential photobiostimulatory effect. However, no significant changes were observed at lower (0.5 W) and higher (2 W) output powers. The area of open tubular space inside the root canal was significantly reduced after irradiation, regardless of the applied power. Additionally, irradiation contributed to the demineralization of the dentin on the inner root walls. Future studies should explore the impact of irrigants used between irradiation cycles, the potential benefits of conical laser tips for more even energy distribution, and a thorough analysis of how disinfection protocols affect both the dentin structure and stem cell viability. Full article

FLASH radiotherapy is a novel irradiation modality that employs ultra-high mean dose rates exceeding 40–150 Gy/s, far surpassing the typical ~0.03 Gy/s used in conventional radiotherapy. This advanced technology delivers high doses of radiation within milliseconds, effectively targeting tumors while minimizing damage to the surrounding healthy tissues. However, the precise mechanism that differentiates responses between tumor and normal tissues is not yet understood. This study primarily examines the ROD hypothesis, which posits that oxygen undergoes transient radiolytic depletion following a radiation pulse. We developed a computational model to investigate the effects of dose rate on radiolysis in an aqueous environment that mimics a confined cellular space subjected to instantaneous pulses of energetic protons. This study employed the multi-track chemistry Monte Carlo simulation code, IONLYS-IRT, which has been optimized to model this radiolysis in a homogeneous and aerated medium. This medium is composed primarily of water, alongside carbon-based biological molecules (RH), radiation-induced bio-radicals (R^●), glutathione (GSH), ascorbate (AH⁻), nitric oxide (^●NO), and α-tocopherol (TOH). Our model closely monitors the temporal variations in these components, specifically focusing on oxygen consumption, from the initial picoseconds to one second after exposure. Simulations reveal that cellular oxygen is transiently depleted primarily through its reaction with R^● radicals, consistent with prior research, but also with glutathione disulfide radical anions (GSSG^●−) in roughly equal proportions. Notably, we show that, contrary to some reports, the peroxyl radicals (ROO^●) formed are not neutralized by recombination reactions. Instead, these radicals are rapidly neutralized by antioxidants present in irradiated cells, with AH⁻ and ^●NO proving to be the most effective in preventing the propagation of harmful peroxidation chain reactions. Moreover, our model identifies a critical dose rate threshold below which the FLASH effect, as predicted by the ROD hypothesis, cannot fully manifest. By comparing our findings with existing experimental data, we determine that the ROD hypothesis alone cannot entirely explain the observed FLASH effect. Our findings indicate that antioxidants might significantly contribute to the FLASH effect by mitigating radiation-induced cellular damage and, in turn, enhancing cellular radioprotection. Additionally, our model lends support to the hypothesis that transient oxygen depletion may partially contribute to the FLASH effect observed in radiotherapy. However, our findings indicate that this mechanism alone is insufficient to fully explain the phenomenon, suggesting the involvement of additional mechanisms or factors and warranting further investigation. Full article

Exposure to ionizing radiation (IR) poses a significant risk for all organisms. Although plants are generally more resistant than animals, radiation still impacts their structure and function. Plant resistance to ionizing radiation is a pivotal property to guarantee their survival. This study evaluates bean leaves’ early and long-term responses to oxidative stress induced by ionizing radiation. To assess the early response, we measured a battery of photosynthetic efficiency and oxidative stress markers after exposure of dwarf bean plants to X-ray doses of 0.3, 10, 50, and 100 Gy. We observed that doses started to impact photosynthetic activity at 50 Gy and that markers aggregate in two kinds of behaviors. To test the capacity to recover from radiation-induced damages, 50 Gy-irradiated plants were evaluated with the same markers 3-, 10-, 12-, and 20-days post-irradiation. Dwarf beans displayed remarkable resilience, recovering photosynthetic activity to pre-stress level after three days and pigment content after ten days. The remodulation of oxidative stress markers is slower and more complex, with catalase and total polyphenols failing to recover completely and residual antioxidant activity after twenty days. Despite that, PARP activity recovers to pre-irradiation after three days. The restoration of photosynthesis to pre-irradiated conditions highlights the DNA-repairing efficiency of poly(ADP-ribose) polymerase and antioxidant machinery in providing resilience to radiation-induced oxidative stress. Understanding resilience mechanisms sheds light on the ability of plants to survive and thrive in radiation-intense environments, such as space or radioactively contaminated areas. Full article

Epoxy resins are critical materials in aerospace applications, yet their mechanical properties, specifically the tensile modulus, can be significantly compromised when exposed to electron irradiation in space environments. To thoroughly examine this degradation, we developed an integrated research approach combining vacuum electron irradiation experiments with multi-scale simulations. Coarse-grained (CG) and Monte Carlo (MC) methods were employed to generate the necessary models and primary knock-on atom (PKA) data, while molecular dynamics (MD) simulations were conducted to model the irradiation and tensile processes. Our findings reveal that the tensile modulus percentage loss of epoxy resin stabilizes as the irradiation dose approaches 1.0×10¹⁵ eV/cm². The strong agreement between experimental and simulation results validates the accuracy of this methodology. In the epoxy resin systems studied with different degrees of cross-linking, irradiation leads to an increase in the tensile modulus of the low cross-linked structures with a maximum increase of 21.46%, and it leads to a decrease in the tensile modulus of the high cross-linked structures with a maximum decrease of 8.03%. This multi-scale approach has been successfully applied to investigate the trends and causes of tensile modulus changes in epoxy resins after electron irradiation. It can be used to explore the changes in the properties of a wider range of polymers after irradiation. Full article

Space particle radiation induces charging and discharging phenomena in spacecraft dielectric materials, leading to electrostatic discharge (ESD) and electromagnetic pulses (EMP), which pose significant risks to spacecraft electronic systems by causing interference and potential damage. Accurate and timely monitoring of these phenomena, combined with a comprehensive understanding of their underlying mechanisms, is critical for developing effective protection strategies against satellite charging effects. Addressing in-orbit monitoring requirements, this study proposes the design of a compact sleeve monopole antenna. Through simulations, the relationships between the antenna’s design parameters and its voltage standing wave ratio (VSWR) are analyzed alongside its critical performance characteristics, including frequency band, gain, radiation pattern, and matching circuit. The proposed antenna demonstrates operation within a frequency range of (28.73–31.25) MHz (VSWR < 2), with a center frequency of 30 MHz and a relative bandwidth of 8.4%. Performance evaluations and simulation-based experiments reveal that the antenna can measure pulse signals with electric field strengths ranging from (−1000 to −80) V/m and (80 to 1000) V/m, centered at 25.47 MHz. It reliably monitors discharge pulses generated by electron irradiation on spacecraft-grade FR4 (Flame-Retardant 4) dielectric materials, providing technical support for the engineering application of discharge research in space environments. Full article

Transparent conductive oxides are essential materials for many optoelectronic applications. For new devices for aerospace and space applications, it is crucial to know how they respond to the space environment. The most important issue in commonly used low-Earth orbits is proton radiation. This study examines the effects of high-energy proton irradiation (226.5 MeV) on thin films of aluminium-doped zinc oxide (AZO) and indium tin oxide (ITO). We use X-ray diffraction and electron microscopy observations to see the changes in the structure and microstructure of the films. The optical properties and homogeneity of the materials are determined by spectrophotometry and spectroscopic ellipsometry (SE). Analysis of the chemical states of the elements with X-ray photoelectron spectroscopy (XPS) gives insight into what proton irradiation changes at the surface of the oxides. All measurements show that ITO is less influenced than AZO. The proton energy and fluence used in this study simulate about a hundred years in low Earth orbit. This research demonstrates that both transparent conductive oxide thin films can function under simulated space conditions, with ITO showing superior resilience. The ITO film was more homogenous in terms of the total thickness measured with SE, had fewer defects and adsorbates present on the surface, as XPS analysis proved, and did not show a difference after irradiation regarding its optical properties, transmission, refractive index, or extinction coefficient. Full article

Light serves as the unique driving force of photosynthesis in plants, yet its intensity varies over time and space, leading to corresponding changes in the photosynthetic rate. Here, the photosynthetic induction response under constant and fluctuating light was examined in naturally occurring saplings of four sun-demanding woody species, Eucalyptus. Ficus macrocarpa L., Hibiscus syriacus L. and Ficus carica L. We aimed to find out the relations among gas exchange parameter adaptions among different species during photosynthetic induction. The net photosynthetic rates (A) versus time course curves were sigmoidal or hyperbolic after the dark-adapted leaves were irradiated by continuous saturated light. Compared with other species, Ficus carica L. have the largest net photosynthesis rate, stomatal conductance to CO₂ (g_sc), and the maximum carboxylation rate (V_cmax) at both the initial and steady photosynthetic state. The initial g_sc (g_sci) was as much as sixfold higher compared to the other shrub, Hibiscus syriacus L. The time required to reach 90% of A (t_A90) was 7–30 min; t_A90 of Ficus carica L. and Ficus macrocarpa L. were lower than that of the other two species. The time required to reach 90% of g_sc (t_gsc90) significantly lagged behind t_A90 among species. Biochemical induction was fast in leaves of Ficus carica L., as about 4 min were needed to reach 90% of V_cmax, while the other species needed 7–18 min. Correlation analysis showed that the t_gsc90 was the main factor in limiting t_A90, especially for Eucalyptus spp. and Hibiscus syriacus L.; g_sci was negatively correlated with t_gsc90 among species. Moreover, time-integrated limitation analysis revealed that g_sc still accounted for the largest limitation in constraining A of Eucalyptus spp. and Hibiscus syriacus L. and Ficus macrocarpa L. Overall, the findings suggest that to enhance the carbon gain by woody species under naturally dynamic light environments, attention should be focused on improving the rate of stomatal opening or initial stomatal conductance. Full article

In the realm of advanced optical fiber sensing (OFS) technologies, Fiber Bragg Grating (FBG) has garnered widespread application in the monitoring of temperature, strain, and external refractive indices, particularly within high-radiation environments such as high-energy physics laboratories, nuclear facilities, and space satellites. Notably, FBGs inscribed using femtosecond lasers are favored for their superior radiation resistance. Among various inscription techniques, the point-by-point (PbP) and line-by-line (LbL) methods are predominant; however, their comparative impacts on radiation durability have not been adequately explored. In this research, FBGs were inscribed on a single-mode fiber using both the PbP and LbL methods, and subsequently subjected to a total irradiation dose of 5.04 kGy (radiation flux of 2 rad/s) over 70 h in a ⁶⁰Co-γ radiation environment. By evaluating the changes in temperature- and strain-sensing performance of the FBG pre-irradiation and post-irradiation, this study identifies a more favorable technique for writing anti-irradiation FBG sensors. Moreover, an analysis into the radiation damage mechanisms in optical fibers, alongside the principles of femtosecond laser inscription, provides insights into the enhanced radiation resistance observed in femtosecond laser-written FBGs. This study thus furnishes significant guidance for the development of highly radiation-resistant FBG sensors, serving as a critical reference in the field of high-performance optical fiber sensing technologies. Full article

Numerous challenges are posed by the extra-terrestrial environment for space farming and various technological growth systems are being developed to allow for microgreens’ cultivation in space. Microgreens, with their unique nutrient profiles, may well integrate the diet of crew members, being a natural substitute for chemical food supplements. However, the space radiation environment may alter plant properties, and there is still a knowledge gap concerning the effects of various types of radiation on plants and specifically on the application of efficient and rapid methods for selecting new species for space farming, based on their radio-resistance. Thus, the hypotheses behind this study were to explore the following: (i) the pattern (if any) of radio-sensitivity/resistance; and (ii) if the morphological parameters in relation with pigment content may be a feasible way to perform a screening of radiation responses among species. To perform this, we irradiated dry seeds of basil, rocket, radish, and cress with iron (⁵⁶Fe; 1550 MeV/(g/cm²)) and carbon (¹²C; 290 MeV/u, 13 keV/µm) heavy ions at the doses of 0.3, 1, 10, 20, and 25 Gy to investigate the growth responses of microgreens to acute radiation exposure in terms of morphological traits and photosynthetic pigment content. Results indicate that the microgreens’ reaction to ionizing radiation is highly species-specific and that radiation is often sensed by microgreens as a mild stress, stimulating the same morphological and biochemical acclimation pathways usually activated by other mild environmental stresses, alongside the occurrence of eustress phenomena. Over extended periods, this stimulus could foster adaptive changes, enabling plants to thrive in space. Full article

The transmission of pathogens via touchscreens is a concern both in medical environments regarding nosocomial infections and in public spaces. This study presents the development of a self-disinfecting touchscreen system and its implementation into an existing medical device. The disinfection was achieved by irradiating UVC light laterally into the quartz front glass of the touchscreen. The system also included a two-stage safety shutdown feature to protect users from UVC exposure. To detect the presence of the user’s hand, a proximity sensor behind the front glass of the touch screen was installed in combination with touch input registration. A rapid disinfection of staphylococci was achieved without compromising usability and user safety. The prototype demonstrated a bacterial reduction of 99.96% or 3.4 (±0.36) log levels in less than 1 s. The results suggest that the technology has the potential to make a significant contribution to reducing the transmission of infections in healthcare settings and beyond. Full article

Free space optical (FSO) communication, which has the potential to meet the demand for high-data-rate communications between satellites and ground stations, requires accurate alignment between the transmitter and receiver to establish a line-of-sight channel link. In this paper, we propose a machine learning (ML)-based approach to reduce beam pointing errors in FSO satellite-to-ground communications subjected to satellite vibration and weak atmospheric turbulence. ML models are utilized to find the optimal gain, which plays a crucial role in reducing pointing error displacement in a closed-loop FSO system. In designing the FSO environment, we employ several system model parameters, including control and system matrix components of the transmitter and receiver, noise parameters for the optical channel, irradiance, and the scintillation index of the signal. To predict the gain matrix of the closed-loop system, ML methods, such as tree-based algorithms, and a 1D convolutional neural network (Conv1D) are applied. Experimental results show that the Conv1D model outperforms other ML methods in gain value prediction, helping to maintain the beam position centered on the receiver aperture, minimizing beam pointing errors. When constructing a closed-loop system based on the Conv1D model, the error variance of the pointing error displacement was obtained as 0.012 and 0.015 in clear weather and light fog conditions, respectively. In addition, this research analyzes the impact of input features in a closed-loop FSO system, and compares the pointing error performance of the closed-loop setup to the conventional open-loop setup under weak turbulence. Full article

Electrical vehicles are finding wide acceptance in the Jordanian transportation market; this has caused an accelerating shift in the emissions of greenhouse gases from the direct burning of fossil fuels consumed by the transportation sector towards the power generation sector. On the other hand, as electric vehicles gain more popularity, an extra load is added to the electrical power generation systems, raising essential concerns such as the capability of the power network to support this massive extra load and the increased emission of greenhouse gases caused by power plants. Studies show that Jordan’s weather is known for being bright, sunny, and very suitable for the generation of electric power from solar energy sources. Therefore, with an infrastructure that can support convenient off-grid charging, a huge burden will be taken off the national grid and the environment. Therefore, this work proposes a basic design for an off-grid PV-covered carport and presents a study of the economics and effectiveness of using such a system to charge electric vehicles owned by the students and employees of the Applied Science Private University. The study is based on actual solar irradiance data collected on-site during university working hours (8 a.m.–5 p.m.) to allow students and employees to charge their electric vehicles from an off-grid carport system while on campus. Space limitations for carport design, initial design cost, return on investment, and annual electricity consumption are discussed to demonstrate the benefits of such a system for both the consumer (convenience and low charging cost) and the power company provider (less load to maintain). Full article

As a prominent focus in high-voltage power devices, SiC MOSFETs have broad application prospects in the aerospace field. Due to the unique characteristics of the space radiation environment, the reliability of SiC MOSFETs concerning single-event effects (SEEs) has garnered widespread attention. In this study, we employed accelerator-heavy ion irradiation experiments to study the degradation characteristics for SEEs of 1.2 kV SiC MOSFETs under different bias voltages and temperature conditions. The experimental results indicate that when the drain-source voltage (V_DS) exceeds 300 V, the device leakage current increases sharply, and even single-event burnout (SEB) occurs. Furthermore, a negative gate bias (V_GS) can make SEB more likely via gate damage and Poole–Frenkel emission (PF), reducing the V_DS threshold of the device. The radiation degradation behavior of SiC MOSFETs at different temperatures was compared and analyzed, showing that although high temperatures can increase the safe operating voltage of V_DS, they can also cause more severe latent gate damage. Through an in-depth analysis of the experimental data, the physical mechanism by which heavy ion irradiation causes gate leakage in SiC MOSFETs was explored. These research findings provide an essential basis for the reliable design of SiC MOSFETs in aerospace applications. Full article