Determination Of Radius Research Articles

Anisotropic quark stars in Einstein-Gauss-Bonnet theory

Recent progress in the determination of both masses and radii of neutron stars has put strong constraints on the equation of state (EoS) above the nuclear saturation density. Within a confining quark matter model, we propose an anisotropic star consisting of a homogeneous and unpaired charge-neutral 3-flavor interacting quark matter with O(ms4) corrections in the context of Einstein-Gauss-Bonnet gravity theory. This generalized model depends only on three free parameters: the bag constant B, the interaction parameter a and the Gauss-Bonnet coupling constant α. Given the underlying EoS, we show the possibility of obtaining the maximal neutron star mass which satisfies the recent observational data for PSR J0751+1807. The numerical analysis of mass-radius relations supports the existence of other massive pulsars with a maximum mass consistent and common radii in the range of R≲(11∼14) Km [1]. Furthermore, we discuss the mass vs central mass density (M−ρc) relation for stability, compactness and binding energy in this gravity theory. Our results thus provide circumstantial evidence in favor of super-massive pulsars in EGB gravity.

Elastic positron–proton scattering at low Q$$^2$$

Systematic differences in the the proton's charge radius, as determined by ordinary atoms and muonic atoms, have caused a resurgence of interest in elastic lepton scattering measurements. The proton's charge radius, defined as the slope of the charge form factor at Q$^2$=0, does not depend on the probe. Any difference in the apparent size of the proton, when determined from ordinary versus muonic hydrogen, could point to new physics or need for the higher order corrections. While recent measurements seem to now be in agreement, there is to date no high precision elastic scattering data with both electrons and positrons. A high precision proton radius measurement could be performed in Hall B at Jefferson Lab with a positron beam and the calorimeter based setup of the PRad experiment. This measurement could also be extended to deuterons where a similar discrepancy has been observed between the muonic and electronic determination of deuteron charge radius. A new, high precision measurement with positrons, when viewed alongside electron scattering measurements and the forthcoming MUSE muon scattering measurement, could help provide new insights into the origins of the proton radius puzzle, and also provide new experimental constraints on radiative correction calculations.

Determination of an Effective Heating Radius in District Heating Systems in terms of Reliability

The paper presents a method developed to determine an effective heating radius (EHR) in district heating systems (DHSs) in terms of reliable heat supply to consumers. The search for EHR for various heating mains from the considered district heating source in DHS involves identifying heat source operation zones in various city areas. At the same time, apart from the search for EHR, the nodal reliability indices are estimated for each consumer and then used (if necessary) to adjust the obtained EHR. The paper briefly discusses some of the practical research results.

Monocrystalline fiber growth technique: New critical radius considerations

Laser-heated pedestal growth (LHPG) is an advantageous technique for crystalline fibers pulling due to its fast growth rate, related to the high axial thermal gradient. However, internal cracks can occur if the radius of the fiber is greater than the so-called thermal critical radius. For this reason, it is important to accurately determine the maximum axial thermal gradient to obtain crystalline fibers free of cracks. Herein, we improved the current method for critical radius determination by considering that the maximum temperature gradient is not present in the liquid/solid interface, but occurs directly on fiber, at a certain distance Δ from the liquid/fiber interface. In order to evaluate such improvement, cracks-free fibers of SrTiO3 (Melting Point = 2353 K) and Al2O3 (2345 K) were grown with this new criterion.

TOI-220 b: a warm sub-Neptune discovered byTESS

ABSTRACTIn this paper, we report the discovery of TOI-220 b, a new sub-Neptune detected by the Transiting Exoplanet Survey Satellite (TESS) and confirmed by radial velocity follow-up observations with the HARPS spectrograph. Based on the combined analysis of TESS transit photometry and high precision radial velocity measurements, we estimate a planetary mass of 13.8 ± 1.0 M⊕ and radius of 3.03 ± 0.15 R⊕, implying a bulk density of 2.73 ± 0.47 $\rm {g\,cm}^{-3}$. TOI-220 b orbits a relative bright (V= 10.4) and old (10.1 ± 1.4 Gyr) K dwarf star with a period of ∼10.69 d. Thus, TOI-220 b is a new warm sub-Neptune with very precise mass and radius determinations. A Bayesian analysis of the TOI-220 b internal structure indicates that due to the strong irradiation it receives, the low density of this planet could be explained with a steam atmosphere in radiative–convective equilibrium and a supercritical water layer on top of a differentiated interior made of a silicate mantle and a small iron core.

Сombined ships stability analysis at the stage of design study

. A method of stability analysis for combined ship (oil carrier/platform ship type) at the stage of design study is presented. It should be noted that not all of ship’s main seaworthiness and operational characteristics are the result of a simple addition of the characteristics of an oil carrier and a platform ship. Their mutual influence takes place, which should be taken into account when analysing the stability in the multivariant optimization problems of internal and external design of such ships. This leads to the requirement to adjust the known methods of stability analysis at the initial stages of ship design, which was the purpose of the present work and its originality.
 Taking into account the multivariance of the task and the hull design type, the stability assessment will be carried out through the analysis of the metacentric height extreme value on the assumption that the requirements of Russian River Register for admissible heeling angle at static wind effect are met. In order to account for nonlinearity of static stability curve when inclining up to the angles of deck immersion into water and emergence of bilge, it is suggested to apply an approximate method of metacentric radius determination.
 The proposed method of combined ship stability assessment is recommended to apply at the stage of justification and analysis of ship’s key elements as a limitation in the problems of mathematical modeling of optimization of such type of ships. The method allows to exclude from further consideration at the design study stage the possible options that do not meet the requirements of seaworthiness.

Formation and dispersal of pyroclasts on the Moon: Indicators of lunar magma volatile contents

We use new estimates of the total content and speciation of volatiles released during the ascent and eruption of lunar mare basalt magma to model the generation and behavior of gas bubbles, the disruption of magma at shallow depth by bubble expansion, and the acceleration and dispersal of the resulting pyroclasts. Lunar eruptions in near-vacuum differ significantly from those on bodies with an atmosphere: 1) exposure to near-zero external pressure maximizes volatile release to form gas bubbles; 2) the infinite potential expansion of the gas bubbles both ensures and maximizes magma fragmentation into pyroclastic liquid droplets with sizes linked to the bubble size distribution; 3) the speeds to which gas and entrained pyroclasts can be accelerated by gas expansion are also maximized. Generation of CO gas bubbles at much greater depths and pressures than bubbles of other volatiles produces bimodal (~120 and 650 μm) total pyroclast size distributions. In the near-vacuum, gas expands to pressures so low that gas-particle interactions enter the Knudsen regime, resulting counter-intuitively in the median grainsize in pyroclastic deposits first increasing, then decreasing, and finally increasing again with increasing distance from the vent, instead of decreasing monotonically as when an atmosphere is present. These complex gas-particle interactions cause clast size distributions to vary in a complex way with distance from the vent and the maximum thickness of the deposit to occur at about 75% of the maximum pyroclast range. Lunar eruptions typically evolve through four stages, which significantly influence gas release patterns. Most volatiles are released during the second, hawaiian-style eruption stage. However, elevated gas concentration can occur both in the short first stage (due to gas accumulation in the dike tip during ascent from the mantle) and in the third and fourth stages (due to reduced volume flux, increased time for gas bubble formation, growth, rise and coalescence, and strombolian activity replacing the hawaiian eruption style). Such gas concentration mechanisms can increase pyroclast ranges by a factor of ~5, but result in very much thinner deposits than if no concentration occurs. Maximum pyroclast range scales essentially linearly with total mass fraction of released volatiles; thus determination of the deposit radius around specific vents can provide data on lunar magma volatile contents. If the volatile inventory of the Apollo 17 orange glass bead picritic magma (~3400 ppm maximum) is typical, maximum ranges of the majority of pyroclasts would have been ~20 km. Such eruptions could explain 79% of the currently recognized pyroclastic deposits on the Moon. A few larger deposits and vents, such as the Aristarchus Plateau Dark Mantle and Cobra Head, suggest higher magma volatile contents. Numerous lunar vents show little evidence of associated pyroclastic deposits. Together, these observations suggest a wide range of volatile contents in lunar basaltic magma mantle source regions.

Angular correlations in two-photon spectroscopy of hydrogen

In the present paper, we consider nonresonant corrections to $ 2s-ns/nd $ transition frequencies in hydrogen for the experiments based on two-photon spectroscopy. A detailed study of angular correlations of quantum interference effects within the framework of rigorous quantum electrodynamics is given. Closed expressions for the resonant two-photon scattering cross sections on an atomic level with dependence on all atomic quantum numbers including fine and hyperfine structure are derived. These expressions are applied for the description of experiments based on two-photon spectroscopy with fixing of incident (outgoing) photon polarizations. We demonstrate that for certain experimental geometry nonresonant corrections could be significant for the determination of Rydberg constant and proton charge radius.

High-accuracy calculation of the deuteron charge and quadrupole form factors in chiral effective field theory

We present a comprehensive analysis of the deuteron charge and quadrupole form factors based on the latest two-nucleon potentials and charge density operators derived in chiral effective field theory. The single- and two-nucleon contributions to the charge density are expressed in terms of the proton and neutron form factors, for which the most up-to-date empirical parametrizations are employed. By adjusting the fifth-order short-range terms in the two-nucleon charge density operator to reproduce the world data on the momentum-transfer dependence of the deuteron charge and quadrupole form factors, we predict the values of the structure radius and the quadrupole moment of the deuteron: $r_{\rm str}=1.9729\substack{+0.0015\\ -0.0012}\ \text{fm},\ Q_d=0.2854\substack{+0.0038\\ -0.0017}\ \text{fm}^2. $ A comprehensive and systematic analysis of various sources of uncertainty in our predictions is performed. Following the strategy advocated in our recent publication Phys. Rev. Lett. 124, 082501 (2020), we employ the extracted structure radius together with the accurate atomic data for the deuteron-proton mean-square charge radii difference to update the determination of the neutron charge radius, for which we find: $r_n^2=-0.105\substack{+0.005\\ -0.006} \, \text{fm}^2$. Given the observed rapid convergence of the deuteron form factors in the momentum-transfer range of $Q \simeq 1-2.5$ fm$^{-1}$, we argue that this intermediate-energy domain is particularly sensitive to the details of the nucleon form factors and can be used to test different parametrizations.

Radiative α7m QED contribution to the helium Lamb shift

We present a derivation of the last unknown part of the $\alpha^7m$ contribution to the Lamb shift of a two-electron atom, induced by the radiative QED effects beyond the Bethe logarithm. This derivation is performed in the framework of nonrelativistic quantum electrodynamics and is valid for the triplet (spin $S = 1$) atomic states. The obtained formulas are free from any divergences and are suitable for a numerical evaluation. This opens a way for a complete numerical calculation of the $\alpha^7m$ QED effects in helium, which will allow an accurate determination of the nuclear charge radius from measurements of helium transition frequencies.

Taylor Dispersion Analysis Coupled to Inductively Coupled Plasma-Mass Spectrometry for Ultrasmall Nanoparticle Size Measurement: From Drug Product to Biological Media Studies.

During past decade, special focus has been laid on ultrasmall nanoparticles for nanomedicine and eventual clinical translation. To achieve such translation, a lot of challenges have to be solved. Among them, size determination is a particularly tricky one. In this aim, we have developed a simple hyphenation between Taylor dispersion analysis and inductively coupled plasma-mass spectrometry (ICP-MS). This method was proven to allow the determination of the hydrodynamic radius of metal-containing nanoparticles, even for sizes under 5 nm, with a relative standard deviation below 10% (with a 95% confidence interval) and at low concentrations. Moreover, its specificity provides the opportunity to perform measurements in complex biological media. This was applied to the characterization of an ultrasmall gadolinium-containing nanoparticle used as a theranostic agent in cancer diseases. Hydrodynamic radii measured in urine, cerebrospinal fluid, and undiluted serum demonstrated the absence of interaction between the particle and biological compounds such as proteins.

The Forming Parameters Study Based on ITER Prototypical Vertical Stability Coil Small Bending Arcs

The vertical stability (VS) coil is a set of circle-shaped multilayer in-vessel coil that is arranged in the vacuum vessel. For International Thermonuclear Experimental Reactor (ITER) prototypical VS coil, to avoid the interference with other in-vessel components some small bending arcs are designed. They are the R600 S-shaped bending arc with the angle of 9.2°, the R600 W-shaped bending arc with the angle of 20.3°, 38.1°, 20.3°, and the R215 S-shaped bending arc with the angle of 53.6°. The forming parameters of these arcs are studied in the article. Given the fact of conductor rebound after bending, the key issues of forming the arcs are to determine the suitable wheel mold radius and rotation angle. With regard to the determination of wheel mold radius, the forming deformation states of conductor under different wheel mold radius are simulated. Then the conductor displacement data after rebound are extracted to acquire the conductor inner and outer arcs fitting equations and the corresponding conductor radii are obtained simultaneously. If the calculated conductor central radius is different with the target value, the wheel mold radius will be adjusted and new simulation is employed. The reiteration work is terminated until the target radius is obtained. Subsequently, the wheel mold radius obtained in the data fitting process is referenced to fabricate the matching wheel mold. And the forming experiment is launched to verify the feasibility of conductor bending based on the above wheel mold radius. As to the determination of wheel mold rotation angle, the bending simulation and data fitting are carried out first. Then the process is repeated continuously until the target bending angle is obtained. Finally, the obtained wheel mold rotation angle is assigned as the preliminary bending angle in the forming experiment. If the forming results fail to satisfy the angle requirement, the preliminary bending angle is adjusted slightly and the forming experiment is performed again until the target bending angle is achieved. In addition, wrinkles are found during the forming process for the R215 S-shaped arc. To deal with the wrinkle issue a series of forming technology are attempted, while nearly all of them seem to be not feasible. Finally, bushing is installed at the outer surface of conductor jacket to reinforce its strength and resist the buckling impact from magnesium oxide (MgO). The forming experiments indicate bushing technology successfully eliminates the large wrinkles on the jacket.

Determination of the proton charge radius from the study of the hydrogen S-energy levels

On the basis of quasipotential method in quantum electrodynamics, the energy interval (3S – 1S) in muonic hydrogen is calculated. The corrections of orders α 3, α 4, α 5, α 6 are taken into account, which are determined by relativistic effects, the effects of vacuum polarization, nuclear structure and recoil, as well as combined corrections. In the leading order proton structure effects are expressed in terms of the charge radius of the proton. In the case of two-photon exchange interaction proton structure corrections are determined by the proton electromagnetic form factors. The value of the energy interval (3S – 1S) can be used for comparison with future experimental data and determining the proton charge radius with greater accuracy.

The CARMENES search for exoplanets around M dwarfs

We report the discovery of a Neptune-like planet (LP 714-47 b, P = 4.05204 d, mb = 30.8 ± 1.5M⊕, Rb = 4.7 ± 0.3 R⊕) located in the “hot Neptune desert”. Confirmation of the TESS Object of Interest (TOI 442.01) was achieved with radial-velocity follow-up using CARMENES, ESPRESSO, HIRES, iSHELL, and PFS, as well as from photometric data using TESS, Spitzer, and ground-based photometry from MuSCAT2, TRAPPIST-South, MONET-South, the George Mason University telescope, the Las Cumbres Observatory Global Telescope network, the El Sauce telescope, the TÜBİTAK National Observatory, the University of Louisville Manner Telescope, and WASP-South. We also present high-spatial resolution adaptive optics imaging with the Gemini Near-Infrared Imager. The low uncertainties in the mass and radius determination place LP 714-47 b among physically well-characterised planets, allowing for a meaningful comparison with planet structure models. The host star LP 714-47 is a slowly rotating early M dwarf (Teff = 3950 ± 51 K) with a mass of 0.59 ± 0.02M⊙ and a radius of 0.58 ± 0.02R⊙. From long-term photometric monitoring and spectroscopic activity indicators, we determine a stellar rotation period of about 33 d. The stellar activity is also manifested as correlated noise in the radial-velocity data. In the power spectrum of the radial-velocity data, we detect a second signal with a period of 16 days in addition to the four-day signal of the planet. This could be shown to be a harmonic of the stellar rotation period or the signal of a second planet. It may be possible to tell the difference once more TESS data and radial-velocity data are obtained.

Quantitative comparison between sub-millisecond time resolution single-molecule FRET measurements and 10-second molecular simulations of a biosensor protein.

Molecular Dynamics (MD) simulations seek to provide atomic-level insights into conformationally dynamic biological systems at experimentally relevant time resolutions, such as those afforded by single-molecule fluorescence measurements. However, limitations in the time scales of MD simulations and the time resolution of single-molecule measurements have challenged efforts to obtain overlapping temporal regimes required for close quantitative comparisons. Achieving such overlap has the potential to provide novel theories, hypotheses, and interpretations that can inform idealized experimental designs that maximize the detection of the desired reaction coordinate. Here, we report MD simulations at time scales overlapping with in vitro single-molecule Förster (fluorescence) resonance energy transfer (smFRET) measurements of the amino acid binding protein LIV-BPSS at sub-millisecond resolution. Computationally efficient all-atom structure-based simulations, calibrated against explicit solvent simulations, were employed for sampling multiple cycles of LIV-BPSS clamshell-like conformational changes on the time scale of seconds, examining the relationship between these events and those observed by smFRET. The MD simulations agree with the smFRET measurements and provide valuable information on local dynamics of fluorophores at their sites of attachment on LIV-BPSS and the correlations between fluorophore motions and large-scale conformational changes between LIV-BPSS domains. We further utilize the MD simulations to inform the interpretation of smFRET data, including Förster radius (R0) and fluorophore orientation factor (κ2) determinations. The approach we describe can be readily extended to distinct biochemical systems, allowing for the interpretation of any FRET system conjugated to protein or ribonucleoprotein complexes, including those with more conformational processes, as well as those implementing multi-color smFRET.

Precision spectroscopy of atomic helium.

Helium is a prototype three-body system and has long been a model system for developing quantum mechanics theory and computational methods. The fine-structure splitting in the 23P state of helium is considered to be the most suitable for determining the fine-structure constant α in atoms. After more than 50 years of efforts by many theorists and experimentalists, we are now working toward a determination of α with an accuracy of a few parts per billion, which can be compared to the results obtained by entirely different methods to verify the self-consistency of quantum electrodynamics. Moreover, the precision spectroscopy of helium allows determination of the nuclear charge radius, and it is expected to help resolve the ‘proton radius puzzle’. In this review, we introduce the latest developments in the precision spectroscopy of the helium atom, especially the discrepancies among theoretical and experimental results, and give an outlook on future progress.

Determination of the mean base circle radius of gears by optical multi-distance measurements

Abstract. The required reliability of wind turbine gearboxes increases the requirements for large gear measurements. Extensive measurements to reliably assess the geometry of large gears in the single micrometer range are necessary. Due to an individually fixed measuring volume, standard methods like coordinate and gear measuring instruments reach their limits for large gears with diameters > 1 m. Therefore, a scalable optical measurement approach consisting of a single sensor in combination with a rotary table for multi-distance measurements with subsequent model-based evaluation of shape parameters of gears is presented. The scalable measurement approach is to be extended to a multisensory system in further work. As a fundamental shape parameter the mean base circle radius using the example of spur gears is determined. The base circle radius is used due to the geometric relationship to further shape parameters for example to the profile slope deviation. The theoretically achievable measurement uncertainty of the mean base circle radius due to sensor noise is estimated to less than 5 µm (k=2) for a small and a large gear, which verifies the scalability of the sensor system. In order to show a general proof of principle, two series of optical measurements on a gear with a diameter of 0.105 m are performed and referenced with a tactile measurement. As a result, random errors of 1.2 µm for k=2 are determined. The remaining systematic deviations to the reference value amount to 4.3 and 1.6 µm, respectively. Hence, the total measurement uncertainty is currently limited by systematic effects, and the defined aim of a total uncertainty of less than 5 µm (k=2) is narrowly missed by 1.5 µm. The random errors of 1.2 µm (k=2) show, however, that an adequate measurement precision is achieved and that the multi-distance measurement approach has the potential to reach the aimed measurement uncertainty with appropriate strategies to compensate for the systematic influences. The experimental and theoretical results prove the principle applicability of the proposed single sensor multi-distance approach for the precise inspection of gears.

Directly imaged exoplanets in reflected starlight: the importance of knowing the planet radius

Context. The direct imaging of exoplanets in reflected starlight will represent a major advance in the study of cold and temperate exoplanet atmospheres. Understanding how basic planet and atmospheric properties may affect the measured spectra is key to their interpretation. Aims. We have investigated the information content in reflected-starlight spectra of exoplanets. We apply our analysis to Barnard’s Star b candidate super-Earth, for which we assume a radius 0.6 times that of Neptune, an atmosphere dominated by H2–He, and a CH4 volume mixing ratio of 5 × 10−3. The main conclusions of our study are however planet-independent. Methods. We set up a model of the exoplanet described by seven parameters including its radius, atmospheric methane abundance, and basic properties of a cloud layer. We generated synthetic spectra at zero phase (full disc illumination) from 500 to 900 nm and a spectral resolution R ~ 125–225. We simulated a measured spectrum with a simplified, wavelength-independent noise model at a signal-to-noise ratio of 10. With a retrieval methodology based on Markov chain Monte Carlo sampling, we analysed which planet and atmosphere parameters can be inferred from the measured spectrum and the theoretical correlations amongst them. We considered limiting cases in which the planet radius is either known or completely unknown, and intermediate cases in which the planet radius is partly constrained. Results. If the planet radius is known, we can generally discriminate between cloud-free and cloudy atmospheres, and constrain the methane abundance to within two orders of magnitude. If the planet radius is unknown, new correlations between model parameters occur and the accuracy of the retrievals decreases. Without a radius determination, it is challenging to discern whether the planet has clouds, and the estimates on methane abundance degrade. However, we find the planet radius is constrained to within a factor of two for all the cases explored. Having a priori information on the planet radius, even if approximate, helps improve the retrievals. Conclusions. Reflected-starlight measurements will open a new avenue for characterizing long-period exoplanets, a population that remains poorly studied. For this task to be complete, direct-imaging observations should be accompanied by other techniques. We urge exoplanet detection efforts to extend the population of long-period planets with mass and radius determinations.

New class of relativistic anisotropic strange star in Vaidya-Tikekar model

A new class of compact cold star with strange matter is obtained in a spheroidal space-time with anisotropic pressure described by Vaidya-Tikekar metric. Considering strange matter equation of state namely $p=\frac{1}{3}(\rho -4B)$ , where $B$ is Bag constant in MIT Bag model, we determine the Mass-Radius relationship for Strange Star in four and higher dimensions using the value of surface density $\rho _{s}=4B$ with the allowed value of $B$ ( $145~\text{MeV} < B^{\frac{1}{4}} <164.4~\text{MeV}$ or equivalently $57.55~\text{MeV}/\text{fm}^{3} < B < 95.11~\text{MeV}/\text{fm}^{3}$ ) with respect to neutron for stable strange matter with zero pressure condition. We found that for a constant $B$ , a limiting value of the radius ( $b$ ) of the star for which geometrical parameter $R$ is real within the allowed range of $B$ as mentioned above. We further note that in four dimension the compactness (ratio of mass to radius) of the star corresponding to the maximum radius is greater than 0.33 in isotropic case and increases when anisotropy increases. In case of five dimensions, we note that same type of nature with different values of compactness is observed. Causality condition holds good through out the star in this model up to a certain values of radius $b$ for which $R$ is real. The information about Mass-to-Radius ratio leads to the determination of total mass, radius and other physical parameters of the stellar configuration.

The FAMU experiment: muonic hydrogen high precision spectroscopy studies

The FAMU experiment aims to measure for the first time the hyperfine splitting of the muonic hydrogen ground state. From this measurement the proton Zemach radius can be derived and this will shed light on the determination of the proton charge radius. In this paper, we describe the scientific goal, the method and the detailed preparatory work. This includes the outcome of preliminary measurements, subsequent refined simulations and the evaluation of the expected results. The experimental setup being built for the measurement of the hyperfine splitting to be performed at the RAL laboratory muon facility is also described.