ABSTRACT
Hyoscyamine 6ß-hydroxylase (H6H) is an iron(II)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenase that produces the prolifically administered antinausea drug, scopolamine. After its namesake hydroxylation reaction, H6H then couples the newly installed C6 oxygen to C7 to produce the drug's epoxide functionality. Oxoiron(IV) (ferryl) intermediates initiate both reactions by cleaving C-H bonds, but it remains unclear how the enzyme switches the target site and promotes (C6)O-C7 coupling in preference to C7 hydroxylation in the second step. In one possible epoxidation mechanism, the C6 oxygen wouldâanalogously to mechanisms proposed for the Fe/2OG halogenases and, in our more recent study, N-acetylnorloline synthase (LolO)âcoordinate as alkoxide to the C7-H-cleaving ferryl intermediate to enable alkoxyl coupling to the ensuing C7 radical. Here, we provide structural and kinetic evidence that H6H does not employ substrate coordination or repositioning for the epoxidation step but instead exploits the distinct spatial dependencies of competitive C-H cleavage (C6 vs C7) and C-O-coupling (oxygen rebound vs cyclization) steps to promote the two-step sequence. Structural comparisons of ferryl-mimicking vanadyl complexes of wild-type H6H and a variant that preferentially 7-hydroxylates instead of epoxidizing 6ß-hydroxyhyoscyamine suggest that a modest (â¼10°) shift in the Fe-O-H(C7) approach angle is sufficient to change the outcome. The 7-hydroxylation:epoxidation partition ratios of both proteins increase more than 5-fold in 2H2O, reflecting an epoxidation-specific requirement for cleavage of the alcohol O-H bond, which, unlike in the LolO oxacyclization, is not accomplished by iron coordination in advance of C-H cleavage.
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Heat stress is an increasing challenge for production animals, particularly in warmer regions of the world. The aim of this study was to compare the fit of three different relationships when modelling respiration rate (RR) and rectal temperature (RT) in animals exposed to increased load. Data from three published studies on finishing pigs, gestating sows and dairy cows were analysed. RR and RT are characterized by being unaffected by increased heat load as long as it is kept below a certain level, and in warmer conditions they increase with increased heat load. As an expression of heat load either the air temperature or the ET (Effective Temperature) was used. The ET unites the effect of air temperature, air humidity and velocity on the animal perception of increased heat load. The relationship between RR and RT and the temperature or the ET was analysed by multiple change point regression and the cubic relationships were modelled. In general, the models provided better fits for RR compared to RT. Relationships with an unaffected piece followed by a quadratic relationship and the cubic relationships performed nearly equally well. Using ET resulted in better correlations than using temperature alone for gestating sows and dairy cows.
Subject(s)
Heat Stress Disorders , Respiratory Rate , Cattle , Animals , Female , Swine , Temperature , Animals, Domestic , Lactation , Body Temperature , Humidity , Heat Stress Disorders/veterinary , Hot TemperatureABSTRACT
A detailed overview of the knowledge gaps in our understanding of the heliospheric interaction with the largely unexplored Very Local Interstellar Medium (VLISM) are provided along with predictions of with the scientific discoveries that await. The new measurements required to make progress in this expanding frontier of space physics are discussed and include in-situ plasma and pick-up ion measurements throughout the heliosheath, direct sampling of the VLISM properties such as elemental and isotopic composition, densities, flows, and temperatures of neutral gas, dust and plasma, and remote energetic neutral atom (ENA) and Lyman-alpha (LYA) imaging from vantage points that can uniquely discern the heliospheric shape and bring new information on the interaction with interstellar hydrogen. The implementation of a pragmatic Interstellar Probe mission with a nominal design life to reach 375 Astronomical Units (au) with likely operation out to 550 au are reported as a result of a 4-year NASA funded mission study.
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BACKGROUND: Microsatellite instability (MSI)/mismatch repair deficiency (dMMR) is a key genetic feature which should be tested in every patient with colorectal cancer (CRC) according to medical guidelines. Artificial intelligence (AI) methods can detect MSI/dMMR directly in routine pathology slides, but the test performance has not been systematically investigated with predefined test thresholds. METHOD: We trained and validated AI-based MSI/dMMR detectors and evaluated predefined performance metrics using nine patient cohorts of 8343 patients across different countries and ethnicities. RESULTS: Classifiers achieved clinical-grade performance, yielding an area under the receiver operating curve (AUROC) of up to 0.96 without using any manual annotations. Subsequently, we show that the AI system can be applied as a rule-out test: by using cohort-specific thresholds, on average 52.73% of tumors in each surgical cohort [total number of MSI/dMMR = 1020, microsatellite stable (MSS)/ proficient mismatch repair (pMMR) = 7323 patients] could be identified as MSS/pMMR with a fixed sensitivity at 95%. In an additional cohort of N = 1530 (MSI/dMMR = 211, MSS/pMMR = 1319) endoscopy biopsy samples, the system achieved an AUROC of 0.89, and the cohort-specific threshold ruled out 44.12% of tumors with a fixed sensitivity at 95%. As a more robust alternative to cohort-specific thresholds, we showed that with a fixed threshold of 0.25 for all the cohorts, we can rule-out 25.51% in surgical specimens and 6.10% in biopsies. INTERPRETATION: When applied in a clinical setting, this means that the AI system can rule out MSI/dMMR in a quarter (with global thresholds) or half of all CRC patients (with local fine-tuning), thereby reducing cost and turnaround time for molecular profiling.
Subject(s)
Colorectal Neoplasms , Microsatellite Instability , Artificial Intelligence , Colorectal Neoplasms/diagnosis , Colorectal Neoplasms/genetics , Colorectal Neoplasms/pathology , DNA Mismatch Repair/genetics , Early Detection of Cancer , HumansABSTRACT
Global warming combined with increased production (i.e. more piglets, more milk and consequently more heat) means that sows are more often challenged by heat stress. The objective was to develop an effective temperature (ET) equation to predict how air temperature, velocity and humidity affect the respiration rate (RR), rectal temperature (RT) and skin temperature (ST) as an expression of heat stress in gestating sows in order to elucidate the relationship between the thermal parameters and the sows' perception of the environment. The experimental room was equipped with a negative pressure ventilation system with diffuse air inlet through the ceiling, electrical heaters, steam generators and dehumidifiers. An air distribution unit was constructed to generate vertical air velocity. A total of 16 gestating sows were exposed to three temperatures (25°C, 29°C and 33°C), two levels of relative humidity (30% and 70%) and three levels of air velocity (0.2 ms-1, 1 ms-1 and 2.5 ms-1). The RR, RT and ST were recorded every 30 min throughout the three 2-h test periods. The estimated effects of humidity and velocity in relation to effect of temperature was nearly independent of whether it was determined from RR or RT, whereas the effect of humidity was much smaller when determined from ST. High coefficients of determination (>0.97) were found for the second order relationship between the estimated ET and RR, RT and ST. An increase in relative humidity from 50 to 70% corresponded to an increase in ET of 0.9°C, while an increase in air velocity from 0.2 to 1.0 ms-1 corresponded to a decrease in ET of 1.2°C. The applied ET equation was useful for expressing the combined effect of temperature, humidity and velocity on animals exposed to heat stress. However, multiplying the effect of velocity by the temperature gradient between the animal and the surrounding air did not improve the estimation.
Subject(s)
Heat-Shock Response , Humidity , Respiratory Rate , Swine/physiology , Temperature , Animals , Body Temperature , Body Temperature Regulation , Female , Hot Temperature , Skin TemperatureABSTRACT
BACKGROUND: Current risk models for renal cell carcinoma (RCC) based on clinicopathological factors are sub-optimal in accurately identifying high-risk patients. Here, we perform a head-to-head comparison of previously published DNA methylation markers and propose a potential prognostic model for clear cell RCC (ccRCC). PATIENTS AND METHODS: Promoter methylation of PCDH8, BNC1, SCUBE3, GREM1, LAD1, NEFH, RASSF1A, GATA5, SFRP1, CDO1, and NEURL was determined by nested methylation-specific PCR. To identify clinically relevant methylated regions, The Cancer Genome Atlas (TCGA) was used to guide primer design. Formalin-fixed paraffin-embedded (FFPE) tissue samples from 336 non-metastatic ccRCC patients from the prospective Netherlands Cohort Study (NLCS) were used to develop a Cox proportional hazards model using stepwise backward elimination and bootstrapping to correct for optimism. For validation purposes, FFPE ccRCC tissue of 64 patients from the University Hospitals Leuven and a series of 232 cases from The Cancer Genome Atlas (TCGA) were used. RESULTS: Methylation of GREM1, GATA5, LAD1, NEFH, NEURL, and SFRP1 was associated with poor ccRCC-specific survival, independent of age, sex, tumor size, TNM stage or tumor grade. Moreover, the association between GREM1, NEFH, and NEURL methylation and outcome was shown to be dependent on the genomic region. A prognostic biomarker model containing GREM1, GATA5, LAD1, NEFH and NEURL methylation in combination with clinicopathological characteristics, performed better compared to the model with clinicopathological characteristics only (clinical model), in both the NLCS and the validation population with a c-statistic of 0.71 versus 0.65 and a c-statistic of 0.95 versus 0.86 consecutively. However, the biomarker model had limited added prognostic value in the TCGA series with a c-statistic of 0.76 versus 0.75 for the clinical model. CONCLUSION: In this study we performed a head-to-head comparison of potential prognostic methylation markers for ccRCC using a novel approach to guide primers design which utilizes the optimal location for measuring DNA methylation. Using this approach, we identified five methylation markers that potentially show prognostic value in addition to currently known clinicopathological factors.
Subject(s)
Carcinoma, Renal Cell/diagnosis , Carcinoma, Renal Cell/genetics , DNA Methylation/genetics , Epigenomics/methods , Kidney Neoplasms/diagnosis , Kidney Neoplasms/genetics , Biomarkers, Tumor/genetics , Humans , Prognosis , Risk AssessmentABSTRACT
The LEXI and SMILE missions will provide soft X-ray images of the Earth's magnetosheath and cusps after their anticipated launch in 2023 and 2024, respectively. The IBEX mission showed the potential of an Energetic Neutral Atom (ENA) instrument to image dayside magnetosheath and cusps, albeit over the long hours required to raster an image with a single pixel imager. Thus, it is timely to discuss the two imaging techniques and relevant science topics. We simulate soft X-ray and low-ENA images that might be observed by a virtual spacecraft during two interesting solar wind scenarios: a southward turning of the interplanetary magnetic field and a sudden enhancement of the solar wind dynamic pressure. We employ the OpenGGCM global magnetohydrodynamics model and a simple exospheric neutral density model for these calculations. Both the magnetosheath and the cusps generate strong soft X-rays and ENA signals that can be used to extract the locations and motions of the bow shock and magnetopause. Magnetopause erosion corresponds closely to the enhancement of dayside reconnection rate obtained from the OpenGGCM model, indicating that images can be used to understand global-scale magnetopause reconnection. When dayside imagers are installed with high-ENA inner-magnetosphere and FUV/UV aurora imagers, we can trace the solar wind energy flow from the bow shock to the magnetosphere and then to the ionosphere in a self-standing manner without relying upon other observatories. Soft X-ray and/or ENA imagers can also unveil the dayside exosphere density structure and its response to space weather.
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PURPOSE: Evidence from cross-sectional studies suggests that higher levels of light-intensity physical activity (LPA) are associated with better health-related quality of life (HRQoL) in colorectal cancer (CRC) survivors. However, these associations have not been investigated in longitudinal studies that provide the opportunity to analyse how within-individual changes in LPA affect HRQoL. We investigated longitudinal associations of LPA with HRQoL outcomes in CRC survivors, from 6 weeks to 2 years post-treatment. METHODS: Data were used of a prospective cohort study among 325 stage I-III CRC survivors (67% men, mean age: 67 years), recruited between 2012 and 2016. Validated questionnaires were used to assess hours/week of LPA (SQUASH) and HRQoL outcomes (EORTC QLQ-C30, Checklist Individual Strength) at 6 weeks, and 6, 12 and 24 months post-treatment. We applied linear mixed regression to analyse longitudinal confounder-adjusted associations of LPA with HRQoL. RESULTS: We observed statistically significant longitudinal associations between more LPA and better global quality of life and physical, role and social functioning, and less fatigue over time. Intra-individual analysis showed that within-person increases in LPA (per 8 h/week) were related to improved HRQoL, including better global quality of life (ß = 1.67, 95% CI 0.71; 2.63; total range scale: 0-100) and less fatigue (ß = - 1.22, 95% CI - 2.37; - 0.07; scale: 20-140). Stratified analyses indicated stronger associations among participants below the median of moderate-to-vigorous physical activity (MVPA) at diagnosis. CONCLUSION: Higher levels of LPA were longitudinally associated with better HRQoL and less fatigue in CRC survivors up to two years post-treatment. Further prospective studies using accelerometer data are necessary to inform development of interventions targeting LPA.
Subject(s)
Exercise/physiology , Fatigue/etiology , Quality of Life/psychology , Aged , Colonic Neoplasms , Colorectal Neoplasms/complications , Cross-Sectional Studies , Female , Humans , Longitudinal Studies , Male , Prospective StudiesABSTRACT
BACKGROUND: Advanced prostate cancer etiology is poorly understood. Few studies have examined associations of anthropometric factors (e.g. early adulthood obesity) with advanced prostate cancer risk. PATIENTS AND METHODS: We carried out pooled analyses to examine associations between body fatness, height, and prostate cancer risk. Among 830 772 men, 51 734 incident prostate cancer cases were identified, including 4762 advanced (T4/N1/M1 or prostate cancer deaths) cases, 2915 advanced restricted (same as advanced, but excluding localized cancers that resulted in death) cases, 9489 high-grade cases, and 3027 prostate cancer deaths. Cox proportional hazards models were used to calculate study-specific hazard ratios (HR) and 95% confidence intervals (CI); results were pooled using random effects models. RESULTS: No statistically significant associations were observed for body mass index (BMI) in early adulthood for advanced, advanced restricted, and high-grade prostate cancer, and prostate cancer mortality. Positive associations were shown for BMI at baseline with advanced prostate cancer (HR = 1.30, 95% CI = 0.95-1.78) and prostate cancer mortality (HR = 1.52, 95% CI = 1.12-2.07) comparing BMI ≥35.0 kg/m2 with 21-22.9 kg/m2. When considering early adulthood and baseline BMI together, a 27% higher prostate cancer mortality risk (95% CI = 9% to 49%) was observed for men with BMI <25.0 kg/m2 in early adulthood and BMI ≥30.0 kg/m2 at baseline compared with BMI <25.0 kg/m2 in early adulthood and BMI <30.0 kg/m2 at baseline. Baseline waist circumference, comparing ≥110 cm with <90 cm, and waist-to-hip ratio, comparing ≥1.00 with <0.90, were associated with significant 14%-16% increases in high-grade prostate cancer risk and suggestive or significant 20%-39% increases in prostate cancer mortality risk. Height was associated with suggestive or significant 33%-56% risks of advanced or advanced restricted prostate cancer and prostate cancer mortality, comparing ≥1.90 m with <1.65 m. CONCLUSION: Our findings suggest that height and total and central adiposity in mid-to-later adulthood, but not early adulthood adiposity, are associated with risk of advanced forms of prostate cancer. Thus, maintenance of healthy weight may help prevent advanced prostate cancer.
Subject(s)
Prostatic Neoplasms , Adult , Body Height , Body Mass Index , Diet , Humans , Male , Proportional Hazards Models , Prospective Studies , Risk Factors , Waist CircumferenceABSTRACT
Tail biting is a welfare and economical concern in modern pig production. One common preventive measure used throughout the world is tail docking, which is generally considered one of the most effective methods for limiting tail biting. However, tail docking is a painful mutilation and systematic tail docking is not allowed in the EU. Therefore, the aim was to compare pig behaviour and the prevalence of tail biting in finishing pigs with intact tails housed in two different pen designs under Danish commercial conditions. PEN1 was a traditional Danish pen and PEN2 was inspired by Swedish finisher pen design and had a larger proportion of solid floor area (PEN1: 1/3 and PEN2: 2/3), reduced group size (PEN1: 15 and PEN2: 12), increased space allowance per head (PEN1: 0.7 m2 and PEN2: 0.89 m2) and straw allocated on the floor (PEN2) whereas straw was provided in a straw rack in PEN1. Tail damage observations were carried out daily by the stockperson and every 2 weeks one trained research technician assessed tail damages according to a tail scoring system. Tail lesions were observed in 51% of PEN1 and in 11% of PEN2 (P < 0.001). PEN1 had higher prevalence of tail damages than PEN2 (23% v. 5%, P < 0.001). Behavioural observations were carried out by the use of video recordings. Pigs in PEN2 tended to spend more time on tail-directed behaviour than pigs in PEN1 (P = 0.07), whereas pigs in PEN1 tended to spend more time on ear-directed behaviour (P = 0.08). Pigs in PEN2 spent more time on straw-directed behaviour compared to pigs in PEN1 (P < 0.001). Pen design did not affect time spent on other penmate-directed behaviour. In addition, the level of welfare between the two pen designs was compared using the Welfare Quality® protocol. PEN2 received an overall score of 'excellent' while PEN1 scored 'enhanced'. PEN2 scored higher on all principles besides 'good health', where PEN1 scored better on lameness and wounds. The main measurements accounting for the differences were water supply, huddling, tail biting, social behaviour and fear of humans. In conclusion, the combination of increased space allowance, increased area of solid flooring, straw allocated onto the floor and reduced group size (PEN2) resulted in fewer tail damaged pigs and a better overall welfare assessment, despite a tendency for more tail-directed behaviour.
Subject(s)
Aggression , Animal Husbandry/methods , Animal Welfare , Bites and Stings/veterinary , Swine , Tail/injuries , Animals , Behavior, Animal , Floors and Floorcoverings , Prevalence , Social Behavior , Video RecordingABSTRACT
OBJECTIVE: To determine whether second-line intraarticular glucocorticoid (IAGC) injection improves outcomes in children with persistently active Lyme arthritis after initial antibiotics. METHODS: We conducted an observational comparative effectiveness study through chart review within 3 pediatric rheumatology centers with distinct clinical approaches to second-line treatment of Lyme arthritis. We primarily compared children receiving second-line IAGC to children receiving a second course of antibiotics alone. We evaluated the risk of developing antibiotic-refractory Lyme arthritis (ARLA) using logistic regression and the time to clinical resolution of Lyme arthritis using Cox regression. RESULTS: Of 112 children with persistently active Lyme arthritis after first-line antibiotics, 18 children received second-line IAGC (13 with concomitant oral antibiotics). Compared to children receiving second-line oral antibiotics alone, children treated with IAGC had similar baseline characteristics but lower rates of ARLA (17% vs 44%; OR 0.3, 95% CI 0.1-0.95; p = 0.04) and faster rates of clinical resolution (HR 2.2, 95% CI 1.2-3.9; p = 0.01). Children in IAGC and oral antibiotic cohorts did not differ in treatment-associated adverse events. Among children receiving second-line IAGC, outcomes appeared similar irrespective of use of concomitant antibiotics. Outcomes were also similar between intravenous (IV) and oral antibiotic-treated cohorts, but older children seemed to respond more favorably to IV therapy. IV antibiotics were also associated with higher rates of toxicity. CONCLUSION: IAGC injection appears to be an effective and safe second-line strategy for persistent Lyme arthritis in children, associated with rapid clinical resolution and reduced need for additional treatment.
Subject(s)
Glucocorticoids/therapeutic use , Lyme Disease/drug therapy , Adolescent , Anti-Bacterial Agents/therapeutic use , Child , Child, Preschool , Female , Glucocorticoids/administration & dosage , Humans , Injections, Intra-Articular , Male , Retreatment , Treatment OutcomeABSTRACT
BACKGROUND AND PURPOSE: Caffeine is associated with a lower risk of some neurological diseases, but few prospective studies have investigated caffeine intake and risk of amyotrophic lateral sclerosis (ALS) mortality. We therefore determined associations between coffee, tea and caffeine intake, and risk of ALS mortality. METHODS: We conducted pooled analyses of eight international, prospective cohort studies, including 351 565 individuals (120 688 men and 230 877 women). We assessed coffee, tea and caffeine intake using validated food-frequency questionnaires administered at baseline. We used Cox regression to estimate study- and sex-specific risk ratios and 95% confidence intervals (CI) for ALS mortality, which were then pooled using a random-effects model. We conducted analyses using cohort-specific tertiles, absolute common cut-points and continuous measures of all exposures. RESULTS: During follow-up, 545 ALS deaths were documented. We did not observe statistically significant associations between coffee, tea or caffeine intake and risk of ALS mortality. The pooled multivariable risk ratio (MVRR) for ≥3 cups per day vs. >0 to <1 cup per day was 1.04 (95% CI, 0.74-1.47) for coffee and 1.17 (95% CI, 0.77-1.79) for tea. The pooled MVRR comparing the highest with the lowest tertile of caffeine intake (mg/day) was 0.99 (95% CI, 0.80-1.23). No statistically significant results were observed when exposures were modeled as tertiles or continuously. CONCLUSIONS: Our results do not support associations between coffee, tea or total caffeine intake and risk of ALS mortality.
Subject(s)
Amyotrophic Lateral Sclerosis/mortality , Caffeine , Coffee , Risk Assessment , Tea , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Prospective StudiesABSTRACT
Sirtuin 1 (SIRT1) is an energy-sensing protein, which may affect tumorigenesis. We used SIRT1 variants as time-independent indicators of SIRT1 involvement in carcinogenesis and we studied two tagging SIRT1 variants in relation to colorectal cancer (CRC) risk. We also evaluated known energy balance-related CRC risk factors within SIRT1 genotype strata. The Netherlands Cohort Study includes 120,852 individuals and has 20.3 years follow-up (case-cohort: nsubcohort = 5000; nCRC cases = 4667). At baseline, participants self-reported weight, weight at age 20, height, trouser/skirt size reflecting waist circumference, physical activity, and early life energy restriction. SIRT1 rs12778366 and rs10997870 were genotyped in toenail DNA available for ~75% of the cohort. Sex- and subsite-specific Cox hazard ratios (HRs) showed that the rs12778366 CC versus TT genotype decreased CRC and colon cancer risks in women (HRCRC = 0.53, 95% confidence interval: 0.30-0.94) but not men. Multiplicative interactions were observed between SIRT1 variants and energy balance-related factors in relation to CRC endpoints, but the direction of associations was not always conform expectation nor specific to one genotype stratum. In conclusion, these results support SIRT1 involvement in colon cancer development in women. No conclusions could be made regarding a modifying effect of SIRT1 variants on associations between energy balance-related factors and CRC risk.
Subject(s)
Colorectal Neoplasms/genetics , Polymorphism, Single Nucleotide , Sirtuin 1/genetics , Aged , Body Mass Index , Cohort Studies , Female , Genetic Predisposition to Disease , Humans , Male , Middle Aged , Netherlands , Self Report , Sex Factors , Waist CircumferenceABSTRACT
Saturn has a sufficiently strong dipole magnetic field to trap high-energy charged particles and form radiation belts, which have been observed outside its rings. Whether stable radiation belts exist near the planet and inward of the rings was previously unknown. The Cassini spacecraft's Magnetosphere Imaging Instrument obtained measurements of a radiation belt that lies just above Saturn's dense atmosphere and is decoupled from the rest of the magnetosphere by the planet's A- to C-rings. The belt extends across the D-ring and comprises protons produced through cosmic ray albedo neutron decay and multiple charge-exchange reactions. These protons are lost to atmospheric neutrals and D-ring dust. Strong proton depletions that map onto features on the D-ring indicate a highly structured and diverse dust environment near Saturn.
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Several reports have shown that doctoral and postdoctoral trainees in biomedical research pursue diverse careers that advance science meaningful to society. Several groups have proposed a three-tier career taxonomy to showcase these outcomes. This three-tier taxonomy will be a valuable resource for institutions committed to greater transparency in reporting outcomes, to not only be transparent in reporting their own institutional data but also to lend greater power to a central repository.
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Gel dosimeters are attractive detectors for radiation therapy, with properties similar to biological tissue and the potential to visualize volumetric dose distributions. Radio-fluorogenesis is the yield of fluorescent chemical products in response to energy deposition from ionizing radiation. This report shares the development of a novel radio-fluorogenic gel (RFG) dosimeter, gelatin infused with coumarin-3-carboxlyic acid (C3CA), for the quantification of imparted energy. Aqueous solutions exposed to ionizing radiation result in the production of hydroxyl free radicals through water radiolysis. Interactions between hydroxyl free radicals and coumarin-3-carboxylic acid produce a fluorescent product. 7-hydroxy-coumarin-3-carboxylic acid has a blue (445 nm) emission following ultra-violet (UV) to near UV (365â»405 nm) excitation. Effects of C3CA concentration and pH buffers were investigated. The response of the RFG was explored with respect to strength, type, and exposure rate of high-energy radiation. Results show a linear dose response relationship independent of energy and type, with a dose-rate dependency. This report demonstrates increased photo-yield with high pH and the utility of gelatin-RFG for phantom studies of radiation dosimetry.
ABSTRACT
To achieve breakthroughs in the areas of heliospheric and magnetospheric energetic neutral atom (ENA) imaging, a new class of instruments is required. We present a high angular resolution ENA imager concept aimed at the suprathermal plasma populations with energies between 0.5 and 20 keV. This instrument is intended for understanding the spatial and temporal structure of the heliospheric boundary recently revealed by Interstellar Boundary Explorer instrumentation and the Cassini Ion and Neutral Camera. The instrument is also well suited to characterize magnetospheric ENA emissions from low-altitude ENA emissions produced by precipitation of magnetospheric ions into the terrestrial upper atmosphere, or from the magnetosheath where solar wind protons are neutralized by charge exchange, or from portions of the ring current region. We present a new technique utilizing ultrathin carbon foils, 2-D collimation, and a novel electron optical design to produce high angular resolution (≤2°) and high-sensitivity (≥10-3 cm2 sr/pixel) ENA imaging in the 0.5-20 keV energy range.
ABSTRACT
Energetic charged particle detectors characterize a portion of the plasma distribution function that plays critical roles in some physical processes, from carrying the currents in planetary ring currents to weathering the surfaces of planetary objects. For several low-resource missions in the past, the need was recognized for a low-resource but highly capable, mass-species-discriminating energetic particle sensor that could also obtain angular distributions without motors or mechanical articulation. This need led to the development of a compact Energetic Particle Detector (EPD), known as the "Puck" EPD (short for hockey puck), that is capable of determining the flux, angular distribution, and composition of incident ions between an energy range of ~10 keV to several MeV. This sensor makes simultaneous angular measurements of electron fluxes from the tens of keV to about 1 MeV. The same measurements can be extended down to approximately 1 keV/nucleon, with some composition ambiguity. These sensors have a proven flight heritage record that includes missions such as MErcury Surface, Space ENvironment, GEochemistry, and Ranging and New Horizons, with multiple sensors on each of Juno, Van Allen Probes, and Magnetospheric Multiscale. In this review paper we discuss the Puck EPD design, its heritage, unexpected results from these past missions and future advancements. We also discuss high-voltage anomalies that are thought to be associated with the use of curved foils, which is a new foil manufacturing processes utilized on recent Puck EPD designs. Finally, we discuss the important role Puck EPDs can potentially play in upcoming missions.