Lactate dehydrogenase (LDH) is a cytoplasmic enzyme found in most cells. Increased LDH levels are a nonspecific measure of cellular injury and may be prognostically important in heart failure (HF). This study aims to assess the relationship between LDH and clinical characteristics and outcomes in heart failure with reduced ejection fraction (HFrEF). Using data from GALACTIC-HF, a phase 3, randomized, placebo-controlled trial evaluating the efficacy and safety of omecamtiv mecarbil (OM) in patients with HFrEF, the relationship between LDH and clinical outcomes was analyzed. The incremental value of LDH added to a validated prognostic model (PREDICT-HF) was also calculated using Harrell's C statistic, integrated discrimination index (IDI), and net reclassification index (NRI). In GALACTIC-HF, baseline LDH data were available for 8,179 patients, including 6,138 outpatients. Patients with higher LDH were more frequently female and had worse HF status. They were also more likely to have elevated serum creatinine, liver enzymes, creatine kinase, NT-proBNP, and high-sensitivity troponin I. Compared with patients in the lowest LDH (Q1: 155 U/L [25th-75th percentile: 144-163 U/L]), the HRs for the primary outcome (first HF event or cardiovascular death) were Q2: 183 U/L (25th-75th percentile: 177-188 U/L); HR: 1.15 [95% CI: 1.02-1.31 Hazard ratio does not have unit]; Q3: 207 U/L (25th-75th percentile: 201-215 U/L); HR: 1.39 [95% CI: 1.23-1.58]; and Q4: 253 U/L (25th-75th percentile: 236-280 U/L); HR: 1.84 [95% CI: 1.62-2.08], respectively. Even after adjustment, elevated LDH remained independently associated with higher HR. When added to the PREDICT-HF risk model, baseline LDH improved Harrell's C statistic, IDI, and NRI for the primary outcome. In GALACTIC-HF, higher LDH levels were independently associated with a higher risk of clinical outcomes in HFrEF. (Global Approach to Lowering Adverse Cardiac Outcomes Through Improving Contractility in Heart Failure [GALACTIC-HF]; NCT02929329; EudraCT number: 2016-002299-28).
Omecamtiv mecarbil (OM) has been shown to benefit individuals with heart failure and reduced ejection fraction but the clinical experience of cardiac myosin activators and risk of life-threatening ventricular arrhythmias (VA) is limited. We investigated the effects of OM on incidence of VA, cardiac arrest, and sudden death (SD) in the GALACTIC-HF trial. GALACTIC-HF was a placebo-controlled randomized trial testing the efficacy and safety of OM in participants with symptomatic chronic HF and LVEF ≤35%. Ventricular arrhythmias and cardiac arrest were investigator-reported adverse events while SD was centrally adjudicated. Severe HF was defined according to the ESC-HFA criteria. The effect of OM on the composite of the first occurrence of serious VA, cardiac arrest, or SD was examined using Cox proportional hazards models. Over a median follow-up of 21.8 months, 706 out of the 8232 participants randomized in the GALACTIC-HF trial experienced serious VA, cardiac arrest, or SD. Randomization to OM led to a trend towards reduced risk for the composite arrhythmic outcome (377 events in the placebo group vs. 329 in the OM study arm; HR 0.86; 95% CI 0.75-1.00; P = .054). The strength of the association between OM and lower risk of composite events was stronger in participants with an LVEF ≤the median level of 28% (HR 0.77; 95% CI 0.63-0.94; P = .009) and appeared consistent in participants with severe HF. In this post hoc analysis of the GALACTIC-HF trial, we observed a potential reduction in life-threatening arrhythmia, cardiac arrest, and SD with OM treatment, especially in patients with severely reduced LVEF. These findings require prospective validation in the ongoing COMET-HF trial.
Given the emerging role of transcatheter valve repair in HFrEF patients with moderate/severe secondary mitral regurgitation (MR), we evaluated the prevalence and outcomes related to MR in the GALACTIC-HF trial. The randomized GALACTIC-HF trial compared the efficacy and safety of omecamtiv mecarbil to placebo in 8232 patients with HFrEF, with a primary composite outcome of a first HF event or cardiovascular death. Of 7998 patients (97.2%) with baseline data on MR, 5782 (72.3%) had no MR, 970 (12.1%) had mild MR, and 1221 (15.3%) had moderate MR (only 25 had severe MR). Patients with moderate MR had a higher risk of the primary outcome than those without MR (adjusted HR 1.11; 95% CI 1.01-1.23); risk was not higher in patients with mild MR. The association between moderate MR and the primary outcome was most prominent in patients with less severe HF (milder NYHA class, higher LVEF, and lower N-terminal pro-B-type natriuretic peptide) compared to more severe HF. In adjusted analyses, MR was not associated with mortality, and the results of all analyses remained consistent after including patients with severe MR. The beneficial treatment effect of omecamtiv mecarbil versus placebo on clinical outcomes was not modified by MR. Over 80% of patients with moderate/severe MR fulfilled the broad inclusion criteria for COAPT and RESHAPE-HF2. In GALACTIC-HF, almost 15% of patients with heart failure and reduced ejection fraction had moderate MR, which was associated with a higher risk of the primary outcome.
We argue that ^{23}Na is a potentially significant source of galactic axions. For temperatures ≳7×10^{8}  K-characteristic of carbon burning in the massive progenitors of supernovae and ONeMg white dwarfs-the 440 keV first excited state of ^{23}Na is thermally populated, with its repeated decays pumping stellar energy into escaping axions. Odd-A nuclear abundances are typically very low in high-temperature stellar environments (or absent entirely due to burn-up). ^{23}Na is an exception: ≈0.1M_{⊙} of the isotope is synthesized during carbon burning then maintained at ≈10^{9}  K for times ranging up to 6×10^{4}  yr. Using MESA simulations, a galactic model, and sampling over progenitor masses, locations, and evolutionary stages, we find a continuous flux at Earth of ⟨ϕ_{a}⟩≈22/cm^{2} s for g_{aNN}^{eff}=10^{-9}. Some fraction of these axions converts to photons as they propagate through the galactic magnetic field, producing a distinctive 440 keV line γ-ray detectable by all-sky detectors like the Compton Spectrometer and Imager (COSI). Assuming a 1  μG galactic magnetic field and a sufficiently light axion mass, we find that COSI will be able to probe |g_{aNN}^{eff}g_{aγγ}|≳1.8×10^{-22}  GeV^{-1} at 3σ after two years of surveying.
Dipstick urine testing is often performed in primary and secondary care, although the results may not be routinely inspected or acted upon. We aimed to examine the prognostic value of semiquantitative urine dipstick proteinuria (DP) assessments in patients with heart failure (HF) and reduced ejection fraction. This retrospective analysis utilized data from GALACTIC-HF, a randomized trial that investigated the efficacy and safety of the cardiac myosin activator, omecamtiv mecarbil, compared with placebo in patients with HF with reduced ejection fraction. The primary outcome was the composite of a first HF event (hospitalization or urgent visit for HF) or cardiovascular death, and secondary outcomes were a HF event, cardiovascular death, and all-cause death. Cox proportional hazard models were used to examine the relationship between DP levels and clinical outcomes. Baseline DP data were available for 7790 patients, of whom 5910 (75.9%) had a negative test or trace proteinuria, 995 (12.8%) had 1+, and 885 (11.4%) had ≥2+ proteinuria. The incidence rate of the primary outcome (per 100 person-years) increased significantly with increasing DP: negative/trace (21.8, 95% confidence interval 20.8-22.7); 1+ (34.8, 31.8-38.0); and ≥2+ (38.1, 34.7-41.9). Similar trends were observed for the components of the primary outcome and all-cause mortality. The association between greater DP and worse outcomes was stronger in patients with preserved (≥60 ml/min/1.73 m2) estimated glomerular filtration rate compared with reduced estimated glomerular filtration rate (<60 ml/min/1.73 m2). In GALACTIC-HF, higher DP levels were independently associated with increased risk of adverse clinical outcomes in patients with reduced ejection fraction. GALACTIC-HF ClinicalTrials.gov Identifier: NCT02929329; EudraCT number, 2016-002299-28.
In regions of the Solar System distant from planetary magnetic fields, galactic cosmic rays (GCRs) have generally been assumed to be uniformly distributed over the Earth-Moon distance. However, our analysis of data from the LND (Lunar Lander Neutron and Dosimetry) experiment onboard the Chang'E-4 lander revealed a region of reduced GCR flux in the prenoon sector of the lunar orbit. Further investigation suggests the presence of an energetic particle cavity, formed by Earth's magnetic field acting as an obstacle to GCR propagation. This cavity indicates that the influence of Earth's magnetic field within the space environment extends unexpectedly up to and far beyond the lunar orbit. This finding offers the potential to avoid high radiation levels during future lunar exploration and deep-space missions.
Active galactic nuclei (AGN) with broad emission line regions (BLRs) contain rapidly growing supermassive black holes. Their masses are typically derived from BLR gas motions inferred from spectra and BLR sizes estimated from the AGN luminosity. The breathing BLR model predicts that the spectral line width should change as luminosity varies, keeping mass estimates constant. Here, we present observations of an AGN sample at redshift <0.1 with two epochs separated by 20 years. On average, we find that luminosity and mass estimates vary by a factor of 2, showing a long-term mean-reversion pattern, while the line widths remain constant. A constant line width suggests that full BLRs do not change size during continuum or line flux variability, naturally explaining why scaling relations depend on instantaneously measured Eddington ratios. As a result, we find that single-epoch masses with the best repeatability after 20 years are obtained when sizes are estimated from the narrow [OIII] λ5007Å emission line luminosity.
Background: Spaceflight stressors, including microgravity-induced unloading and galactic cosmic radiation (GCR), acutely disrupt mitochondrial function and contribute to skeletal muscle atrophy. The long-term remodeling of skeletal muscle following combined unloading and radiation exposure remains poorly understood. We investigated protein abundance changes 9-months post-exposure to combined unloading and radiation exposure. Methods: Female, 6-month old, C57Bl/6J mice underwent 5 days of hindlimb unloading (HU) or weight-bearing (WB) conditions, followed by 0Gy, 0.5Gy, or 1.5Gy of simulated GCR exposure using the simplified 5-ion beam exposure (simGCRsim) (n=5/group). The gastrocnemius muscle was collected after 9-months of WB and analyzed by data-independent acquisition mass spectrometry. Differentially abundant proteins were identified and evaluated using pathway enrichment analyses. Results: WB mice exposed to 0.5Gy exhibited increased abundance of electron transport system proteins and mitochondrial transport proteins, suggesting increased mitochondrial activity relative to control mice. HU mice exposed to 0.5Gy displayed decreased glycolytic proteins, increased reliance on oxidative pathways, and reduced antioxidant proteins (glutaredoxins, peroxiredoxin) compared to WB0.5. In HU mice, a higher radiation dose (HU1.5 vs HU0.5) led to the downregulation of 26S proteasome subunits and the upregulation of peroxisomal antioxidant, tricarboxylic acid cycle, and β-oxidation proteins, indicating dose-dependent mitochondrial adaptations. Conclusion: Long-term muscular remodeling after simGCRsim exposure is influenced by both muscle loading status and radiation dose, with prolonged shifts toward oxidative metabolism and altered protein quality control persisting months after exposure. These findings provide new insights into skeletal muscle adaptation to spaceflight stressors and have important implications for astronaut health during and after long-duration missions.
To reproduce observed galaxy properties, cosmological simulations require that massive galaxies experience feedback from active galactic nuclei, which regulates star formation within those galaxies. However, the energetics and timescales of these feedback processes are poorly constrained. We combined optical, infrared, submillimeter, and radio observations of the active galaxy VV 340a, which is hosting a low-power jet launched from a supermassive black hole at its center. We found that the jet undergoes precession, with a period of (8.2 ± 5.5) × 105 years, and drives an outflow of gas at a rate of 19.4 ± 7.9 solar masses per year. The jet shocks the gas, producing highly ionized plasma that extends several kiloparsecs from the nucleus. The outflow ejects sufficient gas from the galaxy to influence its star-formation rate.
We study the formation of stellar bars using 145 simulations of disc galaxies embedded in live and static dark matter haloes. We use the exponential bar growth time-scale, [Formula: see text], to quantify how disc structure and kinematics regulate the onset and rate of secular bar formation. We extend previous work to thicker and more turbulent discs, motivated by those observed at high redshift ([Formula: see text]). By revisiting several commonly used disc stability criteria - the Efstathiou-Lake-Negroponte parameter ([Formula: see text]), the Ostriker-Peebles ratio ([Formula: see text]), and the disc stellar mass fraction within 2.2 disc scale radii ([Formula: see text]) - we find that [Formula: see text], when expressed in terms of the disc's orbital period, follows a tight power law with each criteria. In Milky Way-like discs embedded in live haloes, bars form within a Hubble time if [Formula: see text], [Formula: see text], and [Formula: see text]. We show discs with higher velocity dispersion experience delayed bar growth and introduce an empirical relation that correctly describes the bar formation time-scales of all our live halo models. Bars in static haloes grow at roughly half the rate of those in live haloes and require substantially greater disc instability to do so.
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Future Artemis-class missions to Mars will expose astronauts to prolonged space radiation (SR), sleep disruption, and operational demands requiring greater autonomy, placing decision making and executive function at heightened risk. Both SR and sleep fragmentation (SF) independently impair cognition, yet their combined effects remain poorly understood. Using the Associative Recognition Memory and Interference (ARMIT) task, we assessed cognitive performance in male rats exposed to 10 cGy of Galactic Cosmic Ray simulation (GCRsim), SF, or both. Under well-rested conditions, GCRsim-exposed rats exhibited overt deficits in the C.1.2 stage, performing at chance when reinforcement contingencies shifted, consistent with impaired cognitive flexibility. In contrast, high-performing GCRsim-exposed rats that initially performed comparably to Sham s revealed latent deficits following a single night of SF. Specifically, the SF-induced loss of C.1.3 performance was accompanied by perseverative errors (persistently selecting outdated cues despite negative feedback), reflecting impaired attentional control and decision updating. Sham s maintained stable performance after SF. These findings support a two-hit vulnerability model in which SR primes corticostriatal and frontoparietal networks for collapse under subsequent sleep disruption. Operationally, this suggests that astronauts may display either persistent or stress-induced deficits, with both modes threatening mission success. Identifying mechanisms of such vulnerabilities is essential for countermeasure development.
A valid definition of severe heart failure (HF) is essential for earlier identification, timely referral for advanced therapies, and to optimize clinical trial design. To assess the prevalence, prognostic performance, and 1-year outcomes associated with different definitions of severe and advanced HF (AdvHF) in patients with heart failure with reduced ejection fraction (HFrEF). We included 15,153 patients with EF <40%, HF duration >6 months, and no prior left ventricular assist device or heart transplant, from the Swedish Heart Failure Registry. Several definitions of severe/AdvHF were evaluated: a simplified Heart Failure Association (HFA) definition (NYHA III-IV, EF <30%, ≥2 HF hospitalizations in 12 months), the GALACTIC-Severe-definition (NYHA III-IV, EF <30%, ≥1 hospitalization in 6 months), and variations adding/removing criteria such as NT-proBNP levels and diuretic dose to the HFA-AdvHF definition. Predictive performance and 1-year outcomes were analyzed. The HFA-definition identified 6.4% of patients, with a 1-year cardiovascular death/HF hospitalization risk of 70% and all-cause mortality of 45% (AUC = 0.72). The GALACTIC-Severe definition identified 12.6% of patients with slightly lower but still substantial event rates (59% and 38%, respectively; AUC = 0.73). Definitions incorporating NT-proBNP ≥2000 pg/ml had the highest prognostic accuracy (AUC = 0.75). The HFA-AdvHF definition selected a smaller, high-risk group, while the GALACTIC-Severe criteria identified a broader population, with a lower, but still high risk. NT-proBNP, HF hospitalization history, and diuretic dose might represent valuable enrichment tools for future trials.
Supermassive black hole (SMBH) binary systems are an unavoidable outcome of galaxy mergers. Their dynamics encode valuable information about their formation and growth, the composition of their host galactic nuclei, the evolution of galaxies, and the nature of gravity. Many SMBH binaries with separations pc-kpc have been found, but closer (subparsec) binaries remain to be confirmed. Identifying these systems may elucidate how binaries evolve past the "final parsec" until gravitational radiation drives them to coalescence. Methods to discover and characterize SMBH binaries can shed light on these important questions and potentially open new multimessenger channels. Here we show that SMBH binaries in nonactive galactic nuclei can be identified and characterized by the gravitational lensing of individual bright stars, located behind them in the host galaxy. The rotation of "caustics"-regions where sources are hugely magnified due to the SMBH binary's orbit and inspiral-leads to quasiperiodic lensing of starlight (QPLS). The extreme lensing magnification of individual bright stars produces a significant variation in the host galaxies' luminosity; their lightcurve traces the orbit of the SMBH binary and its evolution, analogous to the waveforms recorded by gravitational-wave (GW) detectors. QPLS probes the population of sources observable by pulsar timing arrays and space detectors (LISA, TianQin), offering advance warning triggers for merging SMBHs for coincident or follow-up GW detections. SMBH population models predict 1-50 [190-5000](n_{⋆}/pc^{-3}) QPLS binaries with period less than 10[40] yr with comparable masses and redshift z<0.3, where n_{⋆} is the stellar number density. Additionally, stellar and orbital motion will lead to frequent instances of single or double flares caused by SMBHBs with longer periods. This novel signature can be searched for in a wealth of existing and upcoming time-domain photometric data: identifying quasiperiodic variability in galactic lightcurves will reveal an ensemble of binary systems and illuminate outstanding questions around them.
Chagas disease, caused by Trypanosoma cruzi parasites, is a common cause of heart failure (HF) in Latin America and has recently been declared endemic in the United States. The authors compared outcomes in Chagasic HF vs ischemic and other nonischemic etiologies of HF with reduced ejection fraction (HFrEF). The aim of this study was to compare clinical outcomes of Chagasic HFrEF vs ischemic and other nonischemic etiologies. Investigator-reported etiology of HFrEF in the ATMOSPHERE, PARADIGM-HF, and GALACTIC-HF trials was categorized as ischemic, valvular, alcoholic, hypertensive, idiopathic, viral, Chagasic, or "other." Time to the composite of first HF hospitalization or cardiovascular death, its components, all-cause death, and stroke was analyzed using Cox models adjusted for baseline characteristics, patient setting, trial, and other potential confounders. Among 23,647 patients (13,381 ischemic, 4,344 idiopathic, 2,559 hypertensive, 1,923 others, 423 alcoholic, 412 valvular, 297 viral, and 308 Chagasic), Chagasic HF had the highest incidence rates of all clinical outcomes compared with other etiologies. Compared with patients with ischemic etiology, the adjusted HRs in Chagasic HF were significantly higher for the composite outcome (HR: 1.65; 95% CI: 1.36-2.02), HF hospitalization (HR: 1.75; 95% CI: 1.36-2.25), cardiovascular death (HR: 1.86; 95% CI: 1.47-2.35), all-cause death (HR: 1.82; 95% CI: 1.47-2.25), and stroke (HR: 2.16; 95% CI: 1.20-3.88). Patients with Chagasic HFrEF have a distinct clinical course associated not only with excess mortality but also with an increased risk for stroke compared with other etiologies except for valvular and "other" etiologies. (Aliskiren Trial to Minimize Outcomes in Patients with Heart Failure [ATMOSPHERE], NCT00853658; Prospective Comparison of ARNI [Angiotensin Receptor-Neprilysin Inhibitor] with ACEI [Angiotensin-Converting-Enzyme Inhibitor] to Determine Impact on Global Mortality and Morbidity in Heart Failure Trial [PARADIGM-HF], NCT01035255; Global Approach to Lowering Adverse Cardiac Outcomes Through Improving Contractility in Heart Failure [GALACTIC-HF], NCT02929329).
The interstellar origin and chemistry of the NCN moiety, a critical molecular backbone of nucleobases, is central to the RNA world hypothesis for the Origins of Life; however, its formation mechanisms under astrophysical conditions remain largely unexplored. Here, we report the first laboratory preparation of cyanamide (NH2CN), a key intermediate in prebiotic chemical evolution, in low-temperature ammonia-methylamine (NH3-CH3NH2) interstellar ice analogs exposed to energetic electrons, simulating secondary electrons generated by galactic cosmic rays. Utilizing tunable vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry combined with isotopic labeling, cyanamide was identified isomer-selectively in the gas phase during temperature-programmed desorption. These findings reveal nonequilibrium pathways to cyanamide in methylamine-containing interstellar ices, highlighting the pivotal role of galactic cosmic rays in forming the biorelevant NCN backbone and shedding light on the abiotic synthesis of nucleobases in astrophysical environments.
This study provides a thorough investigation of the open cluster Czernik 38, employing photometric and astrometric data from Gaia DR3 and 2MASS. Our analysis refines the fundamental parameters of the cluster, including its structure, kinematics, evolutionary status, age, and morphology. To evaluate membership, we utilized the pyUPMASK Python package in conjunction with the HDBSCAN algorithm. The main focus of this research is our novel method of assigning a membership probability at each radius, instead of using a singular value for the entire cluster. One of the main outcomes of our research indicates that there is an elongated structure and a leading tidal tail that aligns with the orbital trajectory of the cluster. This tidal phenomenon arises due to orbital differential rotation. Furthermore, we have discovered a new star cluster located 32 arcmin from the center of Czernik. This cluster may serve as a companion to the Czernik 38 cluster in a binary cluster system or a complex colliding system; we will explore this further in subsequent research. According to Gaia, the distance modulus of the cluster and the color excess [Formula: see text] are measured at 12.69[Formula: see text] 0.08 mag and 2.40 [Formula: see text] 0.04 mas, respectively. Additionally, from 2Mass, the distance modulus is 12.87 [Formula: see text] 0.93 mag, while the color excess [Formula: see text] is 0.89 [Formula: see text] 0.2 mag. Moreover, the cluster age is determined to be 115.0[Formula: see text] 20.3 Myr. The components of proper motion ([Formula: see text], [Formula: see text]) and the parallax ([Formula: see text]) are found as -2.41 [Formula: see text] 0.328 mas yr[Formula: see text], -5.263 [Formula: see text] 1.063 mas yr[Formula: see text], and 0.21 [Formula: see text] 0.083 mas, respectively. The calculated mean Gaia distances are roughly 3580.4 [Formula: see text] 230.5 pc, which is in agreement with the photometric data from the Gaia and 2Mass data, within the error. There are 37 stars that exhibit radial velocity with average 46.1 [Formula: see text] 8.54[Formula: see text], which allows us to derive orbital parameters using the galpy python package. As a result, the cluster is moving parallel to the Galactic plane towards the Galactic center. We have identified a novel category of pre-main sequence stars that form a distinct branch in the right of Color-Magnitude Diagram (CMD). These stars exhibit lower temperatures and surface gravity compared to main sequence stars. This implies that there exists a significant rate of star formation within the Czernik 38 cluster. Furthermore, we have discovered many faint blue stars in Czernik 38, as well as in the newly identified clusters, which could potentially be white dwarf stars.
The simplest sugar-glyceraldehyde (HOCH2CH(OH)CHO)-represents a central molecule in the biochemistry of all lifeforms (glycolysis/gluconeogenesis). Linking photosynthesis and carbon fixation to sugar metabolism is fundamental to the liberation of energy from sugars and is the point at which glycolysis becomes exothermic-the pay-off phase. By exploiting isomer-selective photoionization reflectron time-of-flight mass spectrometry, glyceraldehyde and its energetic enol isomer 1,2,3-propenetriol (HOCH2C(OH)CHOH) are identified in situ during space-simulation experiments as reaction products of radicals formed in ethylene glycol (HOCH2CH2OH) and carbon monoxide (CO) interstellar model ices exposed to energetic electrons as proxies for galactic cosmic rays. Isotopic substitution demonstrates the mechanism of sugar formation from molecules abundant in the interstellar medium. The stability of the carbon-centered radical intermediates formyl (HĊO) and 1,2-dihydroxyethyl (HOCH2ĊHOH) imply that reactions of carbon monoxide and methanol derivatives like ethylene glycol represent a facile, highly active mechanism of sugar production within ice coated interstellar grains in deep space.
Nuclear reaction cross-sections are needed for Monte Carlo and deterministic radiation transport codes used for ion therapy and radiation protection in space. A GSI-ESA-NASA combined effort generated a free and publicly available nucleus-nucleus reaction cross-section database. Nevertheless, protons - the main component of solar particle events and galactic cosmic ray fluences in space - account alone for over 60% of the effective dose behind thick shields in space and are used in 88% of the cancer-treatment ion-therapy centers worldwide. Therefore, in the present work, proton-projectile data have also been included. These data are compared to the reaction cross-section models used in radiation transport codes, including the models of Tripathi-Cucinotta-Wilson, Hybrid-Kurotama, Kox, Shen, and Kox-Shen. The Tripathi-Cucinotta-Wilson model uses the Tripathi99 model for low-Z projectile ions and the Tripathi96 model for other projectiles. The Hybrid-Kurotama model is based on the Black Sphere formula at high energies, which, for proton data, is smoothly connected to the Tripathi99 model at low energies. It is found that the Tripathi99 and Hybrid-Kurotama models best fit the proton-projectile data.
Blue stragglers are anomalously massive core hydrogen-burning stars that, according to the theory of single star evolution, should not exist. They are suspected to form in mass-enhancement processes, involving binary evolution or stellar collisions. In dynamically active systems like globular clusters, the number of blue stragglers originated by collisions is expected to increase with the local density and the rate of stellar encounters. Here we analyze more than 3000 blue stragglers in 48 Galactic globular clusters with different structures, finding that their number normalized to the sampled luminosity anti-correlates (instead of correlating) with the central density, collision rate, and dynamical age of the parent cluster. Similar trends are also found for the cluster binary fraction. Once inserted in the context of the current knowledge of the BSS phenomenon, these correlations indicate that low-density regions (possibly because of a higher binary production/survival rate) are the natural habitat of both BSSs and binary systems, and the observed BSSs mostly have a binary-related origin mediated by the environmental conditions.