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Measurements of the EMC effect in the tritium and helium-3 mirror nuclei are reported. The data were obtained by the MARATHON Jefferson Lab experiment, which performed deep inelastic electron scattering from deuterium and the three-body nuclei, using a cryogenic gas target system and the high resolution spectrometers of the Hall A Facility of the Lab. The data cover the Bjorken x range from 0.20 to 0.83, corresponding to a squared four-momentum transfer Q^{2} range from 2.7 to 11.9  (GeV/c)^{2}, and to an invariant mass W of the final hadronic state greater than 1.84  GeV/c^{2}. The tritium EMC effect measurement is the first of its kind. The MARATHON experimental results are compared to results from previous measurements by DESY-HERMES and JLab-Hall C experiments, as well as with few-body theoretical predictions.
Anisotropic pair breaking close to surfaces favors the chiral A phase of the superfluid ^{3}He over the time-reversal invariant B phase. Confining the superfluid ^{3}He into a cavity of height D of the order of the Cooper pair size characterized by the coherence length ξ_{0}-ranging between 16 nm (34 bar) and 77 nm (0 bar)-extends the surface effects over the whole sample volume, thus allowing stabilization of the A phase at pressures P and temperatures T where otherwise the B phase would be stable. In this Letter, the surfaces of such a confined sample are covered with a superfluid ^{4}He film to create specular quasiparticle scattering boundary conditions, preventing the suppression of the superfluid order parameter. We show that the chiral A phase is the stable superfluid phase under strong confinement over the full P-T phase diagram down to a quasi-two-dimensional limit D/ξ_{0}=1, where D=80  nm. The planar phase, which is degenerate with the chiral A phase in the weak-coupling limit, is not observed. The gap inferred from measurements over the wide pressure range from 0.2 to 21.0 bar leads to an empirical ansatz for temperature-dependent strong-coupling effects. We discuss how these results pave the way for the realization of the fully gapped two-dimensional p_{x}+ip_{y} superfluid under more extreme confinement.
The spin kinetics of adsorbed and liquid 3He in contact with a mixture of LaF3 (99.67 %) and DyF3 (0.33 %) 20 nm powders at temperatures of 1.5-4.2 K in magnetic fields up to 505mT was studied by pulsed nuclear magnetic resonance (NMR). Two-component of nuclear magnetic relaxation was observed in the experiment and theoretical relaxation model was proposed. The possible explanation of this phenomena can be carried out by a model that consider the exchange of magnetization of helium-3 nuclei located in the adsorbed layer and in the bulk of the liquid. The proposed relaxation model can be applied to other systems with the strong influence of adsorbed layer.
Liquid heliums are intriguing substance. Superfluid states below certain critical temperatures, notably liquid helium-4 and helium-3 exhibit ultra-high thermal conductivity ( TC) in the superfluid phase. However, the microscopic origin of the TC of liquid heliums in the normal phase remains unclear. In this work, we employ the thermal resistance network model to calculate the thermal conductivities of normal liquid helium-4 (He I) and helium-3. Predicted values are not only in good agreement with the measurements but also reproduce the experimental trend of TC increasing with temperature and pressure.
Deuterium-deuterium (D-D) neutron spectrum diagnostics in tokamaks are a challenging task with current technologies. To address this issue, we designed and tested a fast and compact helium-3 proportional counter with a diameter of 2.5 cm and an effective length of 15 cm and using Kr as a stopping gas. The detector achieved a resolution of 96 keV for 2.406 MeV neutrons with a pulse shaping of 2 µs. Test results indicate that this detector has the potential to form a D-D neutron spectrometer for tokamaks, composed of detector arrays.
We report on the first observation of diffusion anisotropy of gaseous helium-3 entrapped in ordered aerogels at 4.2 K. The origins of 3He diffusion anisotropy in aerogels of different porosity are discussed. The correlations between gas diffusion coefficient and basic parameters of aerogels, such as porosity, fiber diameter, and fiber's degree of alignment, are inspected using simple diffusion simulations within the framework of classical diffusion model in both oriented and chaotic aerogels under conditions of diffuse (Knudsen diffusion) and specular reflections of atoms from the walls. The failure of the two-phase and Knudsen diffusion models at low temperature in isotropic and anisotropic aerogels is observed. The effect of a wall attractive potential on the gas dynamics is suspected to play a crucial role in the gas diffusion and its anisotropy. The rough theoretical estimates of that effect at low temperatures in aerogel space confirm this assumption. The observed peculiar diffusion is universal and is expected to occur with other probe gases at higher temperatures.
From cyclotron frequency ratios of HD^{+}/^{3}He^{+}, HD^{+}/T^{+}, and T^{+}/^{3}He^{+} we measure the mass difference between atoms of T and ^{3}He to be 1.995 940 8 (23)×10^{-5} u, corresponding to a Q value for tritium β decay of 18 592.071(22) eV. This enables an improved check on systematics of β decay experiments that set limits on neutrino mass. Using the HD^{+} mass calculated from the atomic masses of the proton and deuteron as given by Rau et al. [Nature 585, 43 (2020)NATUAS0028-083610.1038/s41586-020-2628-7], we also obtain improved atomic masses for the triton and helion (considered to be fundamental constants), namely, 3.015 500 716 066 (39) and 3.014 932 246 957 (38) u.
The present review is focused on experimental and theoretical methods together with applications of helium NMR in chemistry and biochemistry. It comprises two main sections, the first dealing with standardization and instrumentation for 3He NMR spectroscopy and the second dealing with its practical applications, mainly those in general and organic chemistry with a special emphasis on the rapidly developing and exciting area of fullerenes encapsulating helium atoms. Several general applications of 3He NMR spectroscopy in physical chemistry and biomedicine are also briefly discussed.
Chronic obstructive pulmonary disease (COPD) and emphysema are characterized by functional and structural damage which increases the spaces for gaseous diffusion and impairs oxygen exchange. Here we explore the potential for hyperpolarized (HP) 3He MRI to characterize lung structure and function in a large-scale population-based study. Participants (n = 54) from the Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study, a nested case-control study of COPD among participants with 10+ packyears underwent HP 3He MRI measuring pAO2, apparent diffusion coefficient (ADC), and ventilation. HP MRI measures were compared to full-lung CT and pulmonary function testing. High ADC values (>0.4 cm2/s) correlated with emphysema and heterogeneity in pAO2 measurements. Strong correlations were found between the heterogeneity of global pAO2 as summarized by its standard deviation (SD) (p < 0.0002) and non-physiologic pAO2 values (p < 0.0001) with percent emphysema on CT. A regional study revealed a strong association between pAO2 SD and visual emphysema severity (p < 0.003) and an association with the paraseptal emphysema subtype (p < 0.04) after adjustment for demographics and smoking status. HP noble gas pAO2 heterogeneity and the fraction of non-physiological pAO2 results increase in mild to moderate COPD. Measurements of pAO2 are sensitive to regional emphysematous damage detected by CT and may be used to probe pulmonary emphysema subtypes. HP noble gas lung MRI provides non-invasive information about COPD severity and lung function without ionizing radiation.
Path integral Monte Carlo simulations and closure computations of quantum fluid triplet structures in the diffraction regime are presented. The principal aim is to shed some more light on the long-standing problem of quantum fluid triplet structures. This topic can be tackled via path integrals in an exact, though computationally demanding, way. The traditional approximate frameworks provided by triplet closures are complementary sources of information that (unexpectedly) may produce, at a much lower cost, useful results. To explore this topic further, the systems selected in this work are helium-3 under supercritical conditions and the quantum hard-sphere fluid on its crystallization line. The fourth-order propagator in the Jang-Jang-Voth's form (for helium-3) and Cao-Berne's pair action (for hard spheres) are employed in the corresponding path integral simulations; helium-3 interactions are described with Janzen-Aziz's pair potential. The closures used are Kirkwood superposition, Jackson-Feenberg convolution, the intermediate AV3, and the symmetrized form of Denton-Ashcroft approximation. The centroid and instantaneous triplet structures, in the real and the Fourier spaces, are investigated by focusing on salient equilateral and isosceles features. To accomplish this goal, additional simulations and closure calculations at the structural pair level are also carried out. The basic theoretical and technical points are described in some detail, the obtained results complete the structural properties reported by this author elsewhere for the abovementioned systems, and a meaningful comparison between the path integral and the closure results is made. In particular, the results illustrate the very slow convergence of the path integral triplet calculations and the behaviors of certain salient Fourier components, such as the double-zero momentum transfers or the equilateral maxima, which may be associated with distinct fluid conditions (e.g., far and near quantum freezing). Closures are shown to yield valuable triplet information over a wide range of conditions, as ascertained from the analyzed centroid structures, which mimic those of fluids at densities higher than the actual ones; thus, closures should remain a part of quantum fluid triplet studies.
The Pomeranchuk effect is a counterintuitive phenomenon where liquid helium-3 (3He) solidifies under specific pressures, not when cooled, but when heated. This behaviour originates from the magnetic entropy of nuclear spins, suggesting a magnetic field should influence it. However, its detailed response to magnetic fields remains elusive due to the small nuclear magneton of 3He and lack of analogous fermion systems. Here, we show that an electron system also exhibit the Pomeranchuk effect, where the Fermi liquid state solidifies in a high magnetic field, unlike conventional electron systems where a field melts an electron solid into a metal. Remarkably, the electron system displays a reentrant liquid state in ultrahigh fields. These responses are explained by changes in magnetic entropy and magnetisation, extending the underlying physics to 3He. Our findings clarify magnetic-field impact on the Pomeranchuk effect and open avenues for magnetic control of chemical interactions.
As quantum computers get bigger, researchers scramble to chill hardware without rare helium-3.
We present the design and performance of a compact, fully cryogen-free cooling platform as a technology demonstrator for quantum hardware applications. The system leverages a four-stage continuous adiabatic demagnetization refrigerator (cADR) to achieve continuous cooling below 30 mK without the use of helium-3. Integrated mechanical and superconducting heat switches enable efficient thermal cycling, while high-density radio frequency (RF) wiring provides the infrastructure required for control and readout of a five-qubit superconducting quantum processor. Housed in a single rack with a spacious, accessible sample stage, the platform demonstrates that cADR technology can be realized in a compact form factor and provides a basis for future quantum hardware platforms operating under stringent space and infrastructure constraints.
This study investigates the comparative performance of foundational models, advanced large-kernel architectures, and traditional deep learning approaches for hyperpolarized gas MRI segmentation across progressive data reduction scenarios. Chronic obstructive pulmonary disease (COPD) remains a leading global health concern, and advanced imaging techniques are crucial for its diagnosis and management. Hyperpolarized gas MRI, utilizing helium-3 (3He) and xenon-129 (129Xe), offers a non-invasive way to assess lung function. We evaluated foundational models (Segment Anything Model and MedSAM), advanced architectures (UniRepLKNet and TransXNet), and traditional deep learning models (UNet with VGG19 backbone, Feature Pyramid Network with MIT-B5 backbone, and DeepLabV3 with ResNet152 backbone) using four data availability scenarios: 100%, 50%, 25%, and 10% of the full training dataset (1640 2D MRI slices from 205 participants). The results demonstrate that foundational and advanced models achieve statistically equivalent performance across all data scenarios (p > 0.01), while both significantly outperform traditional architectures under data constraints (p < 0.001). Under extreme data scarcity (10% training data), foundational and advanced models maintained DSC values above 0.86, while traditional models experienced catastrophic performance collapse. This work highlights the critical advantage of architectures with large effective receptive fields in medical imaging applications where data collection is challenging, demonstrating their potential to democratize advanced medical imaging analysis in resource-limited settings.
The nature of chemical exchange between Earth's core and mantle is fundamental to understanding their evolution. Tungsten-182 and helium-3 anomalies in volcanic rocks from deeply sourced mantle plumes have been attributed to core-mantle exchange. Hydrogen (H) is potentially abundant in the core. Therefore, H may also be a sensitive tracer of core-mantle exchange. We measured 2H/1H ratios (reported as δD) in olivine-hosted basaltic melt inclusions from a Baffin Island lava to test whether mantle plumes contain H from the core. The average δD value (-144 ± 24 per mil) is lower than some estimates for the average depleted upper mantle (δD ≈ -60 ± 20 per mil). The low δD composition likely derives from isotopic diffusion or H leakage from the core, not isotopic fractionation during magmatism or crustal contamination. Over geologic time, core-mantle exchange of H may have overprinted the isotopic composition of mantle plume source regions and much of the upper mantle.
Adiabatic demagnetization refrigeration (ADR) is the only technique capable of reaching ultralow temperatures without helium-3 and plays a crucial role at the forefront of both fundamental and applied science. However, progress in ADR is constrained by the limited magnetic entropy change (-ΔSm) of existing refrigerants at ultralow temperatures. This limitation primarily stems from the inherent contradiction of simultaneously attaining a large -ΔSm and a low magnetic ordering temperature (T0) in magnetic refrigerant design. Here, we show that a magnetic refrigerant exhibiting both a large -ΔSm and a low T0 can be simultaneously achieved by incorporating weak magnetic exchange and dipolar interactions into the dense frustrated magnet KYb3F10 (1). Notably, the average -ΔSm of 1 in the 0.05-1.0 K range surpasses those of commercial refrigerants (NH4)Fe(SO4)2·12H2O and CrK(SO4)2·12H2O by 146 and 219%, respectively, while its T0 is lower than 50 mK. Practical ADR testing confirms that a minimum temperature of 27.2 mK can be reached under a magnetic field of 6 T using 1 as the refrigerant. Thus, this work not only presents a high-performance ultralow-temperature refrigerant but also addresses the long-standing challenge of simultaneously achieving a large -ΔSm and a low T0 in the design of magnetic refrigerants.
Cold atmospheric plasma (CAP) generates reactive oxygen and nitrogen species (ROS/RNS) capable of selectively destroying pathogens and malignant cells while sparing normal tissue. The Canady Helios Cold Plasma (CHCP) HERO (Humidified Electrical Reactive Oxygen) System integrates a CAP generator with a ventilator platform to enable controlled, humidified plasma delivery through the respiratory tract. Efficacy and safety were assessed using A549 human lung carcinoma cells and an in vivo swine model. CAP was delivered with humidified Air/O₂ (1:1 v/v; 2 L·min⁻1) and helium (3 L·min⁻1) at 35–40 V, varying helium humidity (0–100%) and discharge mode (continuous or interval). Cell viability (MTT), ozone (O₃), and ROS/RNS (H₂O₂, NO₂⁻, NO₃⁻) were quantified, and physiological and histological assessments evaluated in vivo safety. A549 viability decreased significantly with increasing helium humidity [ANOVA, F(4, 10) = 1770.23, p = 3.3 × 10⁻14], with > 95% reduction within 5 min at 100% RH. Humidified Air/O₂ reduced O₃ output by 40–60% versus dry gas (p < 0.005). In swine model study, vital signs remained stable and lung histology showed intact alveoli without inflammation or edema; only TNF-α rose modestly (p < 0.05). The CHCP-HERO System achieved complete A549 eradication while maintaining physiological and histological safety, supporting CAP-based ventilation as a promising therapeutic gas system for respiratory infections and lung cancer. The online version contains supplementary material available at 10.1038/s41598-026-47349-1.
Arctic sea-ice loss affects biological productivity, sustenance in coastal communities, and geopolitics. Forecasting these impacts requires mechanistic understanding of how Arctic sea ice responds to climate change, but this is limited by scarce long-term records. We present continuous 30,000-year reconstructions of sea-ice coverage from the Arctic Ocean based on measurements of two isotopes, thorium-230 and extraterrestrial helium-3, whose burial ratio changes with sea-ice coverage. We found that the central Arctic was perennially covered by sea ice during the last glaciation. Sea-ice cover retreated during the deglaciation approximately 15,000 years ago, culminating in seasonal sea-ice coverage in the warm early Holocene, before ice coverage increased into the late Holocene. Sea-ice changes closely correlate with biological nutrient consumption, supporting projections of a nutrient-starved central Arctic Ocean with continued sea-ice loss.
Quantum critical points ubiquitously emerge in strongly correlated systems, with their influence persisting at finite temperatures and external fields. A paradigmatic example is the quantum Ising magnet, where transverse field g controlling quantum fluctuations can expand the quantum critical point into an extended quantum critical regime. In this work, we propose a distinct quantum supercritical regime originating also from the quantum critical point but controlled by the longitudinal field h coupled to the order parameter. Through thermal tensor network simulations, we find the quantum supercritical regime is enclosed by the finite-temperature crossover boundaries T ∝ hzν/Δ, where z, ν and Δ ≡ β + γ are critical exponents. We comprehend the supercritical scaling via thermal data collapse based on the derived scaling form. Amongst other intriguing phenomena in quantum supercritical regime, there exists an enhanced magnetocaloric effect characterized by a universally diverging magnetic Grüneisen ratio Γh ∝ T -Δ/zν, which indicates that a small symmetry-breaking field h can generate dramatic temperature variation. We propose to observe the quantum supercritical regime in the Ising-chain compound CoNb2O6 and related quantum materials, revealing a helium-3-free pathway to millikelvin cooling via the supercritical magnetocaloric effect.
The world needs clean energy. One of the most promising ways of producing it in large amounts is the helium3-deuterium (3 He-D ) fusion reaction. Although there are numerous sources of 3 He on Earth, most of them are either difficult to access or unprofitable to operate. The main problem underlying the shortage of 3 He is the lack of an effective method of obtaining this isotope. Here we report the results of quantum filtration of 3 He from liquid helium in a superfluid state (below the λ -transition), with the use of an entropy filter made of a high-temperature superconductor YBCO-123. During the operation of so-called fountain effect generated with this filter, unlike the other filters, we observed a strong increase of 3 He concentration downstream, where only pure 4 He was expected. This effect occurred due to the unique combination of two quantum phenomena-superfluidity and superconductivity, leading to the observation of a low-temperature rectification-like process. Rectification of helium isotopes does not require lowering the temperature below the λ -transition, so the process can be more economical than filtration. Moreover, micro-superconductors could be applied also to the extraction of deuterium, thus allowing the same method to be used for both crucial components of the 3 He-D fusion. This method should be easy to upscale and could be used in space (with less energy input) as 3 He , the crucial isotope for future energy, is also sought beyond the Earth.