Isotopic dependence of the yield ratios of light fragments from different projectiles and their unified neutron skin thicknesses

The yield ratios of neutron-proton(R(n/p))and^(3)H-^(3)He(R(^(3)H∕^(3)He))with reduced rapidity from 0 to 0.5 were simulated at 50 MeV/u even-even ^(36−56)Ca+^(40)Ca,even-even ^(48−78)Ni+^(58)Ni,and ^(100−139)Sn(every third isotopes)+112 Sn for full reduced impact parameters using the isospin-dependent quantum molecular dynamics(IQMD)model.The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model,which was used for the phase space initialization of the projectile and target in IQMD.We defined the unified neutron skin thickness asΔRnp=<r^(2)>^(1∕2) n−<r^(2)>^(1∕2)p,which was negative for neutron-deficient nuclei.The unifiedΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal,except for extreme neutron-rich isotopes,which is a type of scaling behavior.The yield ratios of the three isotopic chain-induced reactions,which depended on the reduced impact parameter and unified neutron skin thickness,were studied.The results showed that both R(n/p)and R(^(3)H∕^(3)He)decreased with a reduced impact parameter for extreme neutron-deficient isotopes;however,they increased with reduced impact parameters for extreme neutron-rich isotopes,and increased with theΔRnp of the projectiles for all reduced impact parameters.In addition,a scaling phenomenon was observed betweenΔR np and the yield ratios in peripheral colli-sions from different isotopic chain projectiles(except for extreme neutron-rich isotopes).Thus,R(n/p)and R(^(3)H∕^(3)He)from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.

New quantification of symmetry energy from neutron skin thicknesses of^(48)Ca and^(208)Pb

Precise knowledge of the nuclear symmetry energy can be tentatively calibrated using multimessenger constraints.The neutron skin thickness of a heavy nucleus is one of the most sensitive indicators for probing the isovector components of effective interactions in asymmetric nuclear matter.Recent studies have suggested that the experimental data from the CREX and PREX2 collaborations are not mutually compatible with existing nuclear models.In this study,we review the quantification of the slope parameter of the symmetry energy L from the neutron skin thicknesses of^(48)Ca and^(208)Pb.Skyrme energy density functionals classified by various isoscalar incompressibility coefficients K were employed to evaluate the bulk properties of finite nuclei.The calculated results suggest that the slope parameter L deduced from^(208)Pb is sensitive to the compression modulus of symmetric nuclear matter,but not that from^(48)Ca.The effective parameter sets classified by K=220 MeV can provide an almost overlapping range of L from^(48)Ca and^(208)Pb.

Configurational information entropy analysis of fragment mass cross distributions to determine the neutron skin thickness of projectile nuclei

Configurational information entropy(CIE)analysis has been shown to be applicable for determining the neutron skin thickness(δnp)of neutron-rich nuclei from fragment production in projectile fragmentation reactions.The BNN+FRACS machine learning model was adopted to predict the fragment mass cross-sections(σ_(A))of the projectile fragmentation reactions induced by calcium isotopes from ^(36)Ca to ^(56)Ca on a ^(9)Be target at 140MeV/u.The fast Fourier transform was adopted to decompose the possible information compositions inσA distributions and determine the quantity of CIE(S_(A)[f]).It was found that the range of fragments significantly influences the quantity of S_(A)[f],which results in different trends of S_(A)[f]~δnp correlation.The linear S_(A)[f]~δnp correlation in a previous study[Nucl.Sci.Tech.33,6(2022)]could be reproduced using fragments with relatively large mass fragments,which verifies that S_(A)[f]determined from fragmentσAis sensitive to the neutron skin thickness of neutron-rich isotopes.

A possible experimental observable for the determination of neutron skin thickness

The dependence between neutron skin thickness and neutron abrasion cross section （σnabr） for neutron-rich nuclei is investigated within the framework of the statistical abrasion ablation model. Assuming that the density distributions for proton and neutron are of Fermi-type, and adjusting the diffuseness parameter of neutron density distribution in the droplet model, we find out the good linear correlation between the neutron skin thickness and the abrasion cross section σnabr for neutron-rich nuclei. The uncertainty of neutron skin thickness determined from σnabr is very small. It is suggested that σnabr can be used as a new experimental observable to extract the neutron skin thickness for neutronrich nucleus. The scaling behaviours between neutron skin thickness and σnabr, separately, for isotopes of ^26-35Na, ^44-56Ar, ^48-60Ca, ^67-78Ni are also investigated.

Process of Microcellular Propellants with Adjustable Skin Thickness

Microcellular propellants show a vast applicable prospect due to their special shell-pore structure. The effects of saturation pressure and desorption time on skin thickness are studied. The skin thickness is observed and measured using scanning electron microscope (SEM). The results show that the skin thickness decreases when saturation pressure increases from 15 MPa to 30 MPa. In contrast, the skin thickness increases as the desorption time changes from 2 min to 20 min.Therefore, the microcellular propellants with adjustable skin thickness can be obtained under the variable process conditions such as saturation pressure and desorption time.

Exploring nuclear symmetry energy with isospin dependence in neutron skin thickness of nuclei

We propose an alternative way to constrain the density dependence of the symmetry energy from the neutron skin thickness of nuclei which shows a linear relation to both the isospin asymmetry and the nuclear charge with a form of Z2/3. The relation of the neutron skin thickness to the nuclear charge and isospin asymmetry is systematically studied with the data from antiprotonic atom measurement, and with the extended Thomas-Fermi approach incorporating the Skyrme energy density functional. An obviously linear relationship between the slope parameter L of the nuclear symmetry energy and the isospin asymmetry dependent parameter of the neutron skin thickness can be found, by adopting 70 Skyrme interactions in the calculations. Combining the available experimental data, the constraint of -20 MeV 〈～ L 〈～ 82 MeV on the slope parameter of the symmetry energy is obtained. The Skyrme interactions satisfying the constraint are selected.

A revisit to the neutron skin thickness of neutron-rich nuclei in the statistical abrasion ablation model

The cross sections of the fragments produced in the projectile fragmentation reactions of the even calcium isotopes from A=36 to A=52 are calculated using the statistical abrasion ablation model.The neutron skin thickness are studied by investigating the fragments isotopic cross section distributions.The neutron-skin thicknesses of the calcium isotopes have a good linear correlation to the peak positions of their fragment isotopic cross section distributions.The correlation between the neutron skin thickness and the neutron density distributions of 48 Ca is investigated by introducing a parameter to adjust the diffuseness parameter in the fermi-type density distribution.

A new probe of neutron skin thickness

The correlation between neutron-to-proton yield ratio （Rnp） and neutron skin thickness （δnp） in neutron-rich projectile induced reactions is investigated within the framework of the Isospin-Dependent Quantum Molecular Dynamics （IQMD） model. The density distribution of the Droplet model is embedded in the initialization of the neutron and proton densities in the present IQMD model. By adjusting the diffuseness parameter of neutron density in the Droplet model for the projectile, the relationship between the neutron skin thickness and the corresponding Rnp is obtained. The results show strong linear correlation between Rnp and δnp for neutron-rich Ca and Ni isotopes. It is suggested that Rnp may be used as an experimental observable to extract δnp for neutron-rich nuclei, which is very interesting in the study of the nuclear structure of exotic nuclei, the equation of state （EOS） of asymmetric nuclear matter and neutron-rich matter in astrophysics, etc.

Study on the Datong Yak's Skin Development

[Objective] This study was to explore the skin development law of Datong Yak.[Method]Taking Datong yaks at four various growth stages（1 day old,30 days old,180 days old and adult）as experimental materials,we studied histological structure of Datong yak skin by employing the histological methods.[Results]The skins of Datong yak at four various growth stages all showed the characteristics of thinner epidermis and thicker hypodermis,and of less capillary vessels in hypodermis and more pigment cells in epidermis.Datong yak at four various growth stages all showed a fluctuating trend in entire skin thickness,in detail thickening from 1 day old to 30 days old,then thinning to 180 days old,again thickening to adult.[Conclusion]The results provided theoretical basis for further understanding the structural characteristics of Datong yak to adapt to the abominable plateau environment.

Skin Characteristics of Sites Predisposed to Pressure Ulcers among Bedridden Elderly Patients in Japan

Background: Previous studies have not specifically measured skin characteristics at common sites of pressure ulcers in high-risk elderly patients. Therefore, this study aimed to clarify the physiological skin characteristics at common pressure ulcer sites and their relationship with pressure ulcer risk and demographic/laboratory data in bedridden elderly Japanese patients. Methods: This study involved 55 elderly Japanese patients in a long-term care hospital and 25 female Japanese university students. Skin surface temperature, epidermal water content, transepidermal water loss, skin erythema/redness, skin elasticity, and skin thickness were measured using noninvasive devices. The sacral and both heel areas (sites predisposed to pressure ulcers) and mid-to-lower back area (control site) were observed. Results: Elderly patients showed a low epidermal water content at both heels (right heel, 14.8 ± 9.1 arbitrary units, AU.;left heel, 14.4 ± 8.3 AU). Transepidermal water loss remained acceptable at all sites in older patients despite the presence of dry skin (back, 7.1 ± 1.8 g/hm2;sacrum, 7.4 ± 3.0 g/hm2;right heel, 17.7 ± 7.1 g/hm2;left heel, 19.4 ± 8.1 g/hm2). Back (0.61 ± 0.13 AU) and sacral (0.67 ± 0.11 AU) skin elasticity and sacral skin thickness (0.97 ± 0.56 cm) were significantly lower than those of healthy young people (0.86 ± 0.04 AU, 0.87 ± 0.05 AU, and 2.27 ± 0.84 cm, respectively;p < 0.001 for all sites). Moderate positive correlations were observed between back skin elasticity and serum albumin level (r = 0.445, p < 0.001), and between sacral skin thickness and BMI (r = 0.506, p < 0.001) in older patients. Conclusions: Our findings showed that skin thickness and elasticity should be prioritized when evaluating pressure ulcer risk at the sacral region in bedridden elderly Japanese patients. Moreover, skin moisturization should be considered to minimize the risk at the heels in such patients.

Primary contraction of skin grafts:a porcine preliminary study

Aim:Skin grafting is a common clinical practice for plastic surgeons,yet primary contraction of these grafts is a neglected topic.This study was designed to investigate primary contraction and introduce the shape of skin graft as a possible factor that modifies primary contraction behavior,using porcine models.Methods:In the first series,full-thickness skin grafts(FTSGs)and split-thickness skin grafts(STSGs)were compared.In a second series,how the shape of the skin graft affected the degree of contraction was examined.Results:The mean percentage of FTSG shrinkage was 12.04%,and the median was 12.18%.The mean percentage of STSG shrinkage was 6.87%,and the median was 5%.Circle-shaped and square-shaped FTSGs showed mean/median graft shrinkage of 5.83%/6.93%and 4.15%/3.75%,respectively.In STSGs,the circle-shaped and square-shaped grafts had mean/median graft shrinkage of 1.07%/0%and 0.31%/0%,respectively.Conclusion:Our preliminary report revealed an expected greater shrinkage of FTSGs compared with STSGs.Furthermore,in a limited number of specimens,the shape of the skin graft seemed to affect the primary contraction of the STSGs.

Ground-state properties of light kaonic nuclei signaling symmetry energy at high densities

A sensitive correlation between the ground-state properties of light kaonic nuclei and the symmetry energy at high densities is constructed under the framework of relativistic mean-field theory. Taking oxygen isotopes as an example, we see that a high-density core is produced in kaonic oxygen nuclei, due to the strongly attractive antikaonnucleon interaction. It is found that the 1 S_（1/2） state energy in the high-density core of kaonic nuclei can directly probe the variation of the symmetry energy at supranormal nuclear density, and a sensitive correlation between the neutron skin thickness and the symmetry energy at supranormal density is established directly. Meanwhile, the sensitivity of the neutron skin thickness to the low-density slope of the symmetry energy is greatly increased in the corresponding kaonic nuclei. These sensitive relationships are established upon the fact that the isovector potential in the central region of kaonic nuclei becomes very sensitive to the variation of the symmetry energy. These findings might provide another perspective to constrain high-density symmetry energy, and await experimental verification in the future.