Additional Shielding Research Articles

Sequence-Specific Fluorescence Turn-On Sensing of RNA by DNA Probes Incorporating the Tricyclic Cytidine Analogue DEAtC.

Sequence-specific fluorescent probes for RNA are widely used in microscopy applications such as fluorescence in situ hybridization and a growing number of newer approaches to live-cell RNA imaging. The sequence specificity of most of these approaches relies on differential hybridization of the probe to the correct target. Competing sequences with only one or two base mismatches are prone to causing off-target recognition. Here, we report the sequence-specific fluorescent detection of model RNA targets using a tricyclic cytidine analogue DEAtC that is included as a surrogate for natural cytidine in DNA probe strands and that reports directly on Watson-Crick base pairing. The DEAtC-containing DNA oligonucleotide probes exhibit an average 8-fold increase in fluorescence intensity when hybridized to matched RNA with DEAtC base paired with G and little fluorescence turn-on when DEAtC is base paired with A. Duplex structure determination by NMR, time-resolved fluorescence studies, and Stern-Volmer quenching experiments suggest that the combination of greater π stacking and narrower grooves in the A-form DNA-RNA heteroduplex provides additional shielding and favorable electronic interactions between bases, explaining why DEAtC's fluorescence turn-on response to RNA targets is typically 3-fold greater than for DNA targets.

The Relationship between Cancer and Radiation: A New Paradigm.

A key concern with the use of radiation sources (including nuclear power) is the health effects of low levels of radiation, especially the regulatory assumption that every additional increment of radiation increases the risk of cancer (linear no-threshold model, or LNT). The LNT model is nearly a century old. There are dozens if not hundreds of studies showing that this model is incompatible with animal, cellular, molecular, and epidemiological data for low-dose rates in the range of both background radiation levels and much of occupational exposure. The assumption that every increment of radiation equally increases the risk of cancer results in increased physical risks to workers involved with actions to reduce radiation exposure (such as risks from welding additional shielding in place or from additional construction activities to reduce post-closure waste site radiation levels) and avoidance of medical exposure even when radiation treatment has a lower risk than other options such as surgery. One fundamental shortcoming of the LNT model is that it does not account for natural processes that repair DNA damage. However, there is no contiguous mathematical model that estimates cancer risk for both high- and low-dose rates that incorporates what we have learned about DNA repair mechanisms and is sufficiently simple and conservative to address regulatory concerns. The author proposes a mathematical model that dramatically reduces the estimated cancer risks for low-dose rates while recognizing the linear relationship between cancer and dose at high-dose rates.

Progressive technologies of electrophysical treatment for regulation of stress-strain states of elements of welded structures

The development of industry stimulates the development of modern approaches to the optimization of welded structures. The use of pulsed electromagnetic fields, plasma currents, electrodynamic forces and their combined effects is a new trend in engineering practice to improve the mechanical characteristics of metal materials and welded joints (WJ). Treatment with a pulsed electromagnetic field (TwPEMF) is a promising direction for optimizing the stress-strain states (SSS) of welded structures made of non-ferromagnetic metal materials. Using the method of electronic speckle interferometry, the effect of TwPEMF on the SSS of specimens of circumferential WJ with a thickness of δ = 1.0 mm from aluminium AMg6 alloy was investigated. Based on the original procedure using an accelerometer, the kinetics of the action of the force P of the magnetic field pressure on the residual displacements f and SSS of the specimens during their TwPEMF were investigated. TwPEMF of WJ specimens was performed without and with the use of an additional shield made of AMg6 alloy δ = 5.0 mm. It was found that the use of a shield increases the amplitude values of force P by up to two times, which is caused by an increase in the active volume of the conductive medium. At the same time, TwPEMF without and with the use of a shield contributes to the reduction of f values by 2 and 4 times, respectively, and residual SSS by 50 and 80%. On the basis of mathematical modelling, the advantages of using electrodynamic treatment (EDT) of butt WJ δ = 3.0 mm of АMg61 (1561) alloy in the TIG welding process compared to EDT at room temperature (Tk) are substantiated. According to the results of the model verification, it was proved that EDT during TIG contributes to the formation of peak values of residual compressive stresses in the weld zone by 60% more than EDT during Tk. The use of a pulsed barrier discharge (PBD), which generates a low-temperature plasma on the surface of the metal being treated, contributes to the optimization of its structure. An increase in the hardness HV of structural 25KhGNMT steel as a result of its PBD treatment from 420 to 510 units was established, which is accompanied by the dispersion of the metal microstructure.

Measurement of neutron yield for a medical linear accelerator below 10 MV.

The recent trend toward 10MV for volumetric radiotherapy treatment such as volumetric modulated arc therapy (VMAT), stereotactic radiosurgery (SRS), and stereotactic ablative body radiotherapy (SABR) introduces photoneutron production, with implications for non-therapeutic patient dose and additional shielding requirements for treatment room design. The sharply nonlinear drop-off in photoneutron production below 10MV to negligible at 6MV has scarcely been characterized quantitatively, yet can elucidate important practical insights. To measure photoneutron yields in a medical linac at 8MV, which may strike a reasonable balance between usefully increased beam penetration and dose rate as compared to 6MV while reducing photoneutron production which is present at 10MV. A Varian iX linear accelerator undergoing decommissioning at our clinic was made to operate over a range of photon energies between 6 and 15MV by calibrating the bending magnet and adjusting other beam generation parameters. Neutron dose within the treatment room was measured using an Anderson-Braun type detector over a continuum of intermediate energies. The photoneutron production for energies below 10MV was measured, adding to data that is otherwise scarce in the literature. Our results are consistent with previously published results for neutron yield. We found that the photoneutron production at 8MV was about 1/10 of the value at 10MV, and about 10 times higher than detector background at 6MV. Photoneutron production drops off below 10MV, but is still present at 8MV. An 8MV beam is more penetrating than a 6MV beam, and may offer a suitable tradeoff for modern radiotherapy techniques such as VMAT, SRS, and SABR. Further studies are needed to better understand the impact on treatment plan quality between 8 and 10MV beams considering the benefits to facility requirements and non-therapeutic patient dose.

In-situ 3He neutron spin filters at JCNS, status and updates

The JCNS has been developing and using in-situ polarized neutron spin filters for many applications. The system used for analysis on MARIA and polarization for TOPAS were completed about 10 years ago with the MARIA system in standard operation for users and the TOPAS system employed for a long measurement on the POLI instrument. In the meantime we are progressing on several new in-situ polarizers based on these first two but with additional innovations. The KWS-1 analyzer device which was recently used in tests at TU Delft and ISIS is essentially a 50%-sized copy of the MARIA device. The two devices in construction for polarization and analysis on POLI for hot neutrons feature magic-boxes with angled plates on both the entrance and exit sides to minimize overal length and the polarizer device will employ an additional passive magnetic shield of soft iron so that it can operate inside the stray field area of a 8-T vertical (compensated) sample magnet. We will summarize the current status of our 3He neutron spin filters and provide extra focus on the technical aspects and measured performance characteristics of the new devices for KWS-1 and POLI in particular.

A comparative study between pure bismuth/tungsten and the bismuth tungsten oxide for flexible shielding of gamma/X rays

Thermoplastic vulcanizate based flexible W/Bi and bismuth tungsten oxide composites with different doping ratios from 20% to 100% are successfully fabricated. The ray attenuation abilities of the composites are determined at X-ray tube voltages of 80 KVp–120 KVp, and at gamma rays of 59 keV, 122 keV, 343 keV and 960 keV. The surface morphology and elements mapping of W/Bi and bismuth tungsten oxide particles within the polymer have confirmed a more uniform dispersion of bismuth tungsten oxide than W/Bi. Shielding parameters such as transmittance T, mass/linear attenuation coefficients μm and μ, as well as lead equivalent δPb are investigated experimentally and numerically by Monte Carlo code NECP-MCX as well as XCOM program. The transmittance of γ ray decreases exponentially with the areal density of the functional particles, and the best shielding of X-ray goes to 100 KVp tube voltage, followed by 80 KVp and 120 KVp. A comparison of the two series of composites are made that W/Bi always has advantages over bismuth tungsten oxide in attenuation coefficients and lead equivalent, because the extra containing oxygen atoms in bismuth tungsten oxide crystal actually provide very weak additional shielding. Test of mechanical property also reflects the advantage of using pure W/Bi over bismuth tungsten oxide in flexibility. As substitutes for Pb containing materials, these two types of composites could be of potential use in medical diagnosis, interventional surgery, or biological radiation protection, etc.

Microstrip-Fed Dielectric Resonator Circuits Without Shielding

The classic dielectric resonator (DR) circuits require additional metal cavities for the electromagnetic shielding, which leads to a bulky size and difficulty in integration inevitably. To deal with this issue, several approaches have been proposed with the expense of high insertion loss (IL) or poor out-of-band rejection. Inspired by the transmission characteristic theory of DR proposed recently, new low-loss resonant modes are found and further excited by microstrip directly to implement a filter and a filtering power divider in this article. The detailed theoretical analysis and verification have been conducted. For demonstration, two prototypes operating at 3.6 GHz are simulated, fabricated, and measured. The minimum measured IL of the proposed DR filter and filtering power divider is 0.93 and 3.92/3.86 dB, respectively. Comparison between the circuit without and with a metal cavity shows that the low-loss characteristic can be maintained without additional shielding.

Fluoroscopically guided vascular and cardiac transcatheter procedures: a comparison of occupational and patient dose by anatomical region

X-ray guided procedures are being performed by an increasing variety of medical specialties. Due to improvements in vascular transcatheter therapies, there is an increasing overlap of imaged anatomy between medical specialties. There is concern that non-radiology fluoroscopic operators may not have sufficient training to be well informed of the potential implications of radiation exposure and mitigation strategies to reduce dose. This was a prospective, observational, single center study to compare occupational and patient dose levels when imaging different anatomical regions during fluoroscopically guided cardiac and endovascular procedures. Occupational radiation dose was measured at the level of the temple of 24 cardiologists and 3 vascular surgeons (n = 1369), 32 scrub nurses (n = 1307) and 35 circulating nurses (n = 885). The patient dose was recorded for procedures (n = 1792) performed in three angiography suites. Abdominal imaging during endovascular aneurysm repair (EVAR) procedures was associated with a comparatively high average patient, operator and scrub nurse dose despite additional table-mounted lead shields. Air kerma was relatively high for procedures performed in the chest, and chest + pelvis. Higher dose area product and staff eye dose were recorded during procedures of the chest + pelvis due to the use of digital subtraction angiography to evaluate access route prior to/during transaortic valve implantation. Scrub nurses were exposed to higher average radiation levels than the operator during some procedures. Staff should be cognizant of the potentially higher radiation burden to patients and exposed personnel during EVAR procedures and cardiac procedures using digital subtraction angiography.

Evaluation of neutron dose rates at the TCV tokamak facility

A detailed MCNP neutronics model of the building housing the TCV tokamak has been developed. Predicted dose rates have been compared to neutron dose measurements at 12 locations in the building obtained during neutral beam injection into TCV plasmas. This work was motivated both by the necessity to understand neutron transport in a complex environment and to provide an adequate reference model of the building to which additional shielding can be added. The additional shielding is required because of an expected 5-10 fold increase of neutron doses by the addition of a second neutral beam source. The neutron source was estimated using the TRANSP code. Starting from a simple model, which left out or simplified many important structures, the model was iteratively refined. The discrepancies between the predicted and measured doses decreased significantly, down to less than a factor 2 for most of the locations calculated by the most detailed model. A factor 2 is believed to be within the combined errors resulting from uncertainties in the neutron source model, the detector calibration and the uncertainties stemming from the model itself.

X-Ray Protective Aprons Re-Evaluated.

The evaluation of the protective effect of X-ray protective clothing requires new criteria. The current concept assumes more or less uniform covering of the torso with protective material. The frequently worn heavy wrap-around aprons can weigh 7 to 8 kg. As relevant studies show, orthopedic damage can result from long-term activity. It should therefore be investigated whether the apron weight can be reduced by optimizing the material distribution. For a radiobiological evaluation of the protective effect, the "effective dose" should be used. Numerous laboratory measurements were performed with an Alderson Rando phantom as well as dose measurements on clinical personnel. The measurements were supplemented by Monte Carlo simulation of an interventional workplace in which a female ICRP reference phantom was used for the operator. The measured back doses on the Alderson phantom as well as the measured back doses at interventional workplaces were based on the personal equivalent dose Hp(10). Monte Carlo simulations were used to introduce protection factors for the protective clothing based on the "effective dose" introduced in radiation protection. Back doses in clinical radiology personnel are largely negligible. Therefore, back protection can be much lower than currently used or can even be eliminated. The Monte Carlo simulations show that the protective effect of protective aprons worn on the body is higher than when the flat protective material is radiated through (3 D effect). About 80 % of the effective dose is attributed to the body region from the gonads to the chest. By additional shielding of this area, the effective dose can be lowered or, optionally, aprons with less weight can be produced. Attention must also be paid to the "radiation leaks" (upper arms, neck, skull), which can reduce the whole-body protective effect. In the future, the evaluation of the protective effect of X-ray protective clothing should be based on the effective dose. For this purpose, effective dose-based protection factors could be introduced, while the lead equivalent should be used for measurement purposes only. If the results are implemented, protective aprons with approx. 40 % less weight can be produced with a comparable protective effect. · The protective effect of X-ray protective clothing should be described by protection factors based on effective dose.. · The lead equivalent should only be used for measurement purposes.. · More than 80 % of the effective dose is attributed to the body region from the gonads to the chest.. · A reinforcing layer in this area increases the protective effect considerably.. · With optimized material distribution, protective aprons could be up to 40 % lighter.. · Eder H. X-Ray Protective Aprons Re-Evaluated. Fortschr Röntgenstr 2023; 195: 234 - 243.

The new high field septum magnet for upgrading of fast extraction in main ring of J-PARC

The upgrade of the beam power of J-PARC Main Ring to 750 kW by reducing the cycle from 2.48 s to 1.3 s is underway, and the upgrade of the four high-field (HF) septa will be completed by summer of 2023. The operation test of one HF septum, SM31, was conducted in 2020. First trial was 1 Hz operation test, and we confirmed the joule heating at the magnetic coil was lower than limit. Second was magnetic field measurement. We obtained a good linearity between the applied current and the gap field without saturation. The field integral of the gap field was measured to estimate the optimal current for beam extraction, and we found it is 3,400 A. We compared the gap field between in the neutrino line and that in the beam abort line, then we found the longitudinal distributions have a small discrepancy but it was acceptable. The large leakage field was observed around the end-fringes, therefore, in order to reduce the leakage field, we produced an additional duct shield for mounting in the circulating duct in 2022. We verified that the additional duct shield reduced the leakage field to ≈2% of unshielded leakage field. The new SM31 and other two HF septa have been installed in MR by end of May 2022. The beam operation with the new HF septa will be started in June 2022.

Лабораторный стенд на основе СКВИД-магнитометров для исследования магнитных свойств наноматериалов

The laboratory stand with the squid-based gradiometer was developed and tested in experimental studies of magnetic nanoparticles used in medicine. Two versions of the cryogenic probe were tested in investigations, the first of which included an additional XYZ squid-based magnetometer for "electronic" balancing of the input signal gradiometer in a uniform magnetic field. The second probe contained in its design movable trimmers with superconducting plates located in the area of the input loops of the gradiometer for its mechanical balancing. Both cryogenic probes demonstrated stable operation of the squid-based gradiometer at usual laboratory conditions without additional magnetic shielding. The stand was used to study the magnetization of aqueous suspensions of magnetite nanoparticles in various concentrations, which was induced using an uniform magnetic field with an amplitude of up to 15 milliTesla, created by a special system of Helmholtz coils at a frequency range of 4-12 Hz in the vertical and horizontal directions. The magnetic signals of nanoparticles were recorded using a second-order axial gradiometer in a «2:4:2» configuration with an input loop diameter of 8 mm and a base length of 29 mm. The experimental studies of the magnetization of aqueous suspensions of magnetite nanoparticles were aimed at estimating the limiting resolution of the SQUID gradiometer by the number of detected magnetic nanoparticles. The possibility of registering a magnetic signal from about 6 × 109 MNPs of magnetite 6 nm in size in a volume of 1 ml from a distance of about 20 mm from the receiving coils of the gradiometer was demonstrated. Dry liver extracts of small animals containing MNPs were also used as objects of study. Directions of further improvement the used instrumental elements and methods of magnetic measurements for increasing the sensitivity of squid-based gradiometers in experiments with MNPs are determined.

Measures for attenuation of interference at the level of design of the measuring system of spacecraft

One of the primary tasks in the development of temperature control interface modules used as part of onboard equipment for measuring systems on spacecraft for various purposes is to justify a set of measures to ensure their noise immunity, taken at the levels design of the measuring system, measuring device and temperature control interface module. Such a justification involves an assessment of the effectiveness of possible methods for attenuating various types of interference affecting the measuring system, which determine the electromagnetic environment on the spacecraft. The article is devoted to the consideration of interference mitigation measures at the design level of the measuring system, which should be taken to ensure the required noise immunity of the temperature control interface module in combination with measures taken at other design levels. It is shown that in order to ensure the required noise immunity of the temperature control interface modules, it is necessary at the level of the measuring system design to provide for measures to mitigate interference in the power cable and in the measuring cables. In the power cable, it is possible to attenuate interference by reducing the impedance of the common electrostatic shield and the resistance of the connection of the wires of the on-board power buses, as well as by twisting the wires in the form of a twisted pair. In measuring cables, it is possible to attenuate interference by reducing the impedance of the common electrostatic shield and the resistance of communication wires of communication lines, introducing an additional electrostatic shield for individual groups of wires of communication lines, and using pair or quadruple twist in individual groups of wires.

Nuclear Analysis for the Upper Ports in the NB Cell in ITER

In International Thermonuclear Experimental Reactor (ITER), 14 upper ports (UPs) are allocated for diagnostic systems mounted into the port plug. The upper port plug (UPP) consists of the port plug (PP) structure, diagnostic shield module (DSM), and diagnostic first wall (DFW). One of the main functions of the UPP is to provide the neutron shielding to reduce the radiation level in port interspace and the nuclear loads on the superconducting coils. In this work, the nuclear analysis of the UPs #4–#7 that are located in the neutral beam cell is presented. Two configurations have been analyzed with Monte Carlo N-Particle (MCNP) code: the generic UPP design of full shielding (22 tons) and a light version (18 tons) with reduced shielding. The UPP MCNP models have been developed on the basis of latest design files and integrated in a 120° neutral beam injection (NBI) sector extracted from E-lite. Calculations have been performed to evaluate the neutron flux at the port interspace, the nuclear heating of the PP and toroidal field (TF)/poloidal field (PF) coils (TFC/PFC), the neutron flux, and damage for the electrical feedthrough installed on the closure plate with D1SUNED v3.1.4 code. The impact of crosstalk with NBI and neighboring ports has been assessed for neutron flux and shutdown dose rate (SDDR) at 12 days after shutdown. The results of this analysis showed that the impact of the additional shielding of the 22 tons model compared to the 18 tons model is small and limited in space: the fluxes and damage at the electrical feedthrough are about 40%–50% smaller with additional shielding. Analyses enhanced a large radiation crosstalk with NBI ports and a large streaming through the gaps of UPPs.

Dual X-ray- and Neutron-Shielding Properties of Gd2O3/NR Composites with Autonomous Self-Healing Capabilities.

The neutron- and X-ray-shielding, morphological, physical, mechanical, and self-healing properties were investigated for natural rubber (NR) composites containing varying gadolinium oxide (Gd2O3) contents (0, 25, 50, 75, and 100 parts per hundred parts of rubber; phr) to investigate their potential uses as self-healing and flexible neutron- and X-ray-shielding materials. Gd2O3 was selected as a radiation protective filler in this work due to its preferable properties of having relatively high neutron absorption cross-section (σabs), atomic number (Z), and density (ρ) that could potentially enhance interaction probabilities with incident radiation. The results indicated that the overall neutron-shielding and X-ray-shielding properties of the NR composites were enhanced with the addition of Gd2O3, as evidenced by considerable reductions in the half-value layer (HVL) values of the samples containing 100 phr Gd2O3 to just 1.9 mm and 1.3 mm for thermal neutrons and 60 kV X-rays, respectively. Furthermore, the results revealed that, with the increase in Gd2O3 content, the mean values (± standard deviations) of the tensile strength and elongation at break of the NR composites decreased, whereas the hardness (Shore A) increased, for which extreme values were found in the sample with 100 phr Gd2O3 (3.34 ± 0.26 MPa, 411 ± 9%, and 50 ± 1, respectively). In order to determine the self-healing properties of the NR composites, the surfaces of the cut samples were gently pressed together, and they remained in contact for 60 min; then, the self-healing properties (the recoverable strength and the %Recovery) of the self-healed samples were measured, which were in the ranges of 0.30-0.40 MPa and 3.7-9.4%, respectively, for all the samples. These findings confirmed the ability to autonomously self-heal damaged surfaces through the generation of a reversible ionic supramolecular network. In summary, the outcomes from this work suggested that the developed Gd2O3/NR composites have great potential to be utilized as effective shielding materials, with additional dual shielding and self-healing capabilities that could prolong the lifetime of the materials, reduce the associated costs of repairing or replacing damaged equipment, and enhance the safety of all users and the public.

Experimental Verification of Windshields in the Measurement of Low Frequency Noise from Wind Turbines

Measuring noise from wind turbines is a problematic metrological task due to the significant interference caused by the wind, especially in the low-frequency range. In the audible band, especially A-weighted, the impact of interference from wind is considerably less than in the low-frequency and infrasound bands. In the audible band, especially the A-weighted curve, the impact of interference from wind is significantly less than in the low-frequency and infrasound bands. For this reason, methods are still being sought to reduce interference from wind in the lowest frequency bands effectively. Experimental tests within the scope of the work were carried out using several windshields, with a single standard windscreen at 1.5 m and 4 m height, with an additional microphone shield (tent), and on the board with a double windscreen at a ground level according to IEC 61400-11. Experimental verification of a windshield’s effectiveness and impact under real conditions was carried out using a low-frequency noise source, which was the main fan station at the salt mine shaft. This source generates noise with similar spectral characteristics to wind turbines and can operate in windless conditions. This allowed noise measurements to be made without interference from the wind. Signals were recorded in windless and windy conditions at different wind speeds using tested windshields. An effectiveness analysis of the proposed measurement methods was also carried out on the wind farm. Performed research indicates that the best of the tested variants, when measuring wind turbine noise in the low-frequency range, is to place the microphone on the board with a double windscreen according to IEC 61400-11. At wind speeds of less than 5 m/s at 1.5 m above the ground, the shield effectively eliminates disturbances in the band above 4 Hz. Still, as the wind speed increases above 6 m/s, the level of disturbance increases, and its bandwidth in the lowest frequencies expands.

Flexible X-ray imaging detectors using scintillating fibers

We present early design and simulation work on a novel X-ray imaging detector. The intent of the FleX-RAY project is to create a digital X-ray detector that is capable of producing high-resolution images, is flexible enough to produce an image on a curved surface, and is capable of self-reporting its final shape. The X-rays will be detected on a sheet of scintillating optical fibers, which will guide the scintillation light to single-photon avalanche photodiodes. This setup allows the electronics and hardware to be moved out of the path of the X-ray beam, limiting the need for additional shielding. Self-shape-reporting will be achieved using a flexible ultra-thin glass substrate with optical waveguides and Bragg gratings, processed by femtosecond laser point-by-point writing. The functionalized glass substrate allows precise measurement of strains, which can be used to calculate the shape.

Experimental study on the role of polymer addition in Saffman–Taylor instability in miscible flow displacement

The role of nonlinear rheology of polymeric fluids in finger formation and the ensuing morphology of the patterns in miscible flow displacement is examined experimentally. The poly(ethylene oxide) (PEO) is introduced in either displaced or displacing fluid. The PEO solutions exhibit shear-thinning viscosity as well as normal stresses. As viscous fingering is primarily caused by the viscosity contrast between two miscible fluids, the zero-shear viscosities of the two fluids are controlled mainly by their composition. The contribution of rheological behavior in fingering is studied by varying the molecular weight of the polymer. The development of fingering patterns in PEO solutions is observed to be more complex showing more branches and tip-splitting vis-à-vis Newtonian fluid even for the same value of effective viscosity contrast regardless of polymer addition in either fluids. Particularly, flow displacement with displaced PEO solution exhibits significantly intensified patterns such that a fractal-like growth is observed when PEO solution of either high concentration or high molecular weight is being displaced. The additional nonlinear behavior, sidebranching, tip-splitting, and shielding is attributed to the inhomogeneity in fluid viscosity and normal stresses (or elasticity) due to local flow behavior. While shear-thinning behavior promotes the longitudinal growth of fingers leading to the shielding effect, the presence of normal stresses inhibits longitudinal growth of fingers promoting fingers in the transverse direction that imparts tip-splitting. Overall, the nonlinear rheology of the fluids gives rise to the effects, in addition to the viscosity modifications, and hence, is crucial for determining the morphology of the fingering instability.

Dynamic Biasing for Improved On-Orbit Total-Dose Lifetimes of Commercial Electronic Devices

The survivability of microelectronic devices in ionizing radiation environments drives spacecraft design, capability, mission scope, and cost. This article exploits the periodic nature of many space radiation environments to extend device lifetimes without additional shielding or modifications to the semiconductor architecture. We propose a technique for improving component lifetimes through reduced total-dose accumulation by modulating device bias during periods of intense irradiation. Simulation of this “dynamic biasing” technique applied to single-transistor devices in a typical low-Earth orbit results in an increase in component lifetime from 114 to 477 days (318% improvement) at the expense of 5% down time (95% duty cycle). The biasing technique is also experimentally demonstrated using gamma radiation to study three commercial devices spanning a range of integrated circuit complexity in 109- and 256-rad/min dose rate conditions. The demonstrated improvements in device lifetimes using the proposed dynamic biasing technique lay a foundation for more effective use of modern microelectronics for space applications. Analogous to the role real-time temperature monitoring plays in maximizing modern processor performance, the proposed dynamic biasing technique is a means of intelligently responding to the radiation environment and capable of becoming an integral tool in optimizing component lifetimes in space.

Immune dynamics in SARS-CoV-2 experienced immunosuppressed rheumatoid arthritis or multiple sclerosis patients vaccinated with mRNA-1273.

Patients affected by different types of autoimmune diseases, including common conditions such as multiple sclerosis (MS) and rheumatoid arthritis (RA), are often treated with immunosuppressants to suppress disease activity. It is not fully understood how the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific humoral and cellular immunity induced by infection and/or upon vaccination is affected by immunosuppressants. The dynamics of cellular immune reactivation upon vaccination of SARS-CoV-2 experienced MS patients treated with the humanized anti-CD20 monoclonal antibody ocrelizumab (OCR) and RA patients treated with methotrexate (MTX) monotherapy were analyzed at great depth via high-dimensional flow cytometry of whole blood samples upon vaccination with the SARS-CoV-2 mRNA-1273 (Moderna) vaccine. Longitudinal B and T cell immune responses were compared to SARS-CoV-2 experienced healthy controls (HCs) before and 7 days after the first and second vaccination. OCR-treated MS patients exhibit a preserved recall response of CD8+ T central memory cells following first vaccination compared to HCs and a similar CD4+ circulating T follicular helper 1 and T helper 1 dynamics, whereas humoral and B cell responses were strongly impaired resulting in absence of SARS-CoV-2-specific humoral immunity. MTX treatment significantly delayed antibody levels and B reactivation following the first vaccination, including sustained inhibition of overall reactivation marker dynamics of the responding CD4+ and CD8+ T cells. Together, these findings indicate that SARS-CoV-2 experienced MS-OCR patients may still benefit from vaccination by inducing a broad CD8+ T cell response which has been associated with milder disease outcome. The delayed vaccine-induced IgG kinetics in RA-MTX patients indicate an increased risk after the first vaccination, which might require additional shielding or alternative strategies such as treatment interruptions in vulnerable patients. This research project was supported by ZonMw (The Netherlands Organization for Health Research and Development, #10430072010007), the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement (#792532 and #860003), the European Commission (SUPPORT-E, #101015756) and by PPOC (#20_21 L2506), the NHMRC Leadership Investigator Grant (#1173871).