Fusion Barrier Research Articles

Re-investigation of the interplay of fission modes and non-equilibrium fission processes in heavy actinide nuclei 249Bk and 257Md

Measurements of mass and angular distributions of fission fragments from actinide nuclei 249Bk and 257Md, produced in fusion reactions 11B and 19F + 238U, are presented. Experimentally observed mass ratio distributions indicate “multi-chance fission” through the interplay of fission modes in the fission process, and they agree well with predictions from calculations using the GEF (“GEneral description of Fission observables”) model code. Furthermore, to test the signatures of events from non-compound nuclear processes in the fission of 249Bk and 257Md nuclei, Monte Carlo statistical decay model calculations using GEMINI++ were performed for the measured mass distribution at all energies. For comparison purposes, the fission fragment mass distributions of neighboring heavy actinide nuclei, previously measured in the fission of 250Cf and 254Fm nuclei produced by 12C and 16O projectiles on a 238U target, are also presented. The measured angular anisotropy data for the 19F + 238U reaction differ from the results of the Transition State Model (TSM) at energies below the fusion barrier. As a result of the present study, we suggest considering the interplay between K relaxation time, dynamic dissipation, and their influence on shell correction to understand the evolution of fission dynamics in heavy-ion-induced actinide nuclei.

Polarization effects of hot nuclear matter on the fusion of heavy ions

Within the framework of the modified density-dependent Seyler–Blanchard approach in the [Formula: see text] approximation, the polarization effects of hot nuclear matter (PEHNM) are investigated on the fusion process of 16 different colliding systems in the mass range [Formula: see text]. In order to calculate the nucleus–nucleus potential, we use the double-folding (DF) model supplemented with the thermal effects of compound nucleus and also a repulsive potential that takes into account the incompressibility of the nuclear matter. The calculations of the fusion cross-sections are performed based on the couplings to the low-lying [Formula: see text] and [Formula: see text] vibrational states in both target and projectile. The sensitivity of sub-barrier fusion cross-sections to the polarization effects is evident from this study. The obtained results reveal that the modified form of the DF potential in the presence of the PEHNM appropriately reproduces the energy-dependent behavior of the experimental fusion cross-sections for the studied reactions. The role of the polarization effects on the fusion barriers as well as the inner part of the potential is also discussed.

Quantum mechanical treatment of nuclear friction in coupled-channels heavy-ion fusion

Nuclear friction causes energy dissipation in heavy-ion collisions. Its understanding and inclusion in quantum mechanical reaction models are crucial for advancing the physics of heavy-ion reactions forming heavy elements. The effects of nuclear friction on heavy-ion fusion reactions are investigated using the coupled-channels density-matrix method. In this open-quantum-system description, a phenomenological nuclear friction form factor is introduced along with coherent coupled-channels effects. The key nucleus was the 92Zr target, due to its high density of low-lying non-collective excited states, which was recently theorised to be cause of nuclear friction. The calculations using the 16O + 92Zr collision showed that the inclusion of nuclear friction effects increased the fusion probability significantly, and that the agreement between the theoretical and experimental fusion barrier distributions was improved when nuclear friction effects were included.

Influence of saturation property of cold nuclear matter on the parameterization process of fusion barriers

Influence of saturation property of cold nuclear matter on the parameterization process of fusion barriers

Coptidis rhizoma extract alleviates oropharyngeal candidiasis by gC1qR-EGFR/ERK/c-fos axis-induced endocytosis of oral epithelial cells

Ethnopharmacological relevanceCoptidis rhizoma, first recorded in the “Shen Nong's Herbal Classic”, is one of the traditional Chinese medicine (TCM) used to treat infectious diseases, with reputed effectiveness against oropharyngeal candidiasis (OPC). Studies have demonstrated the inhibitory properties of C. rhizoma (CRE) against Candida albicans, yet there is limited information available regarding its treatment mechanism for OPC. Aim of the studyOur previous research has suggested that CRE can prevent the formation of C. albicans hyphae and their invasion of the oral mucosa, thereby exerting a therapeutic effect on OPC. Nevertheless, the precise therapeutic mechanisms remain incompletely understood. Previous studies have revealed that a receptor for globular heads of C1q (gC1qR), a crucial co-receptor of the epidermal growth factor receptor (EGFR), facilitates the EGFR-mediated internalization of C. albicans. Therefore, this study aims to investigate the potential mechanism of action of CRE and its primary component, berberine (BBR), in treating OPC by exploring their effects on the gC1qR-EGFR co-receptor. Materials and methodsTo identify the chemical components of CRE, we utilized Ultra-high performance liquid chromatography in conjunction with quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MSE), revealing the presence of at least 18 distinct components. To observe the therapeutic effects of CRE on OPC at the animal level, we employed hematoxylin and eosin staining, periodic acid-Schiff staining, scanning electron microscopy, and fungal load detection. Subsequently, we evaluated the anti-inflammatory properties of CRE and its main component, BBR, in treating OPC. This was achieved through enzyme-linked immunosorbent assay (ELISA) both at the animal and cellular levels. Additionally, we assessed the ability of C. albicans to disrupt the epithelial barrier of FaDu cells by studying the protective effects of BBR on the fusion barrier using the transwell assay. To further explore the underlying mechanisms, we analyzed the effects of BBR on the gC1qR-EGFR/extracellular signal-regulated kinase/c-Fos signaling pathway at the cellular level using qRT-PCR, western blotting, and immunofluorescence. Furthermore, we validated the effects of BBR on the gC1qR-EGFR co-receptor through ELISA, qRT-PCR, and western blotting. Finally, to confirm the outcomes observed at the cellular level, we validated the impact of CRE on the gC1qR-EGFR co-receptor in vivo using qRT-PCR, western blotting, and immunofluorescence. These comprehensive methods allowed us to gain a deeper understanding of the therapeutic mechanisms of CRE and BBR in treating OPC. ResultsOur findings indicate that CRE and its primary component, BBR, effectively alleviated the symptoms of OPC by modulating the gC1qR-EGFR co-receptor. The chemical composition of CRE and BBR was accurately identified using UPLC-Q/TOF-MSE. The gC1qR-EGFR co-receptor plays a crucial role in regulating downstream signaling pathways, emerging as a potential therapeutic target for OPC treatment. Through both in vitro and in vivo experiments, we explored the therapeutic potential of CRE and BBR in OPC. Additionally, we employed overexpression and silencing techniques to confirm that BBR can indeed influence the gC1qR-EGFR co-receptor and regulate the gC1qR-EGFR/extracellular signal-regulated kinase (ERK)/c-Fos signaling pathway, leading to improved OPC outcomes. Furthermore, the significance of CRE's effect on the gC1qR-EGFR co-receptor was validated in vivo. ConclusionOur study demonstrates that CRE and its main component, BBR, can effectively alleviate OPC symptoms by targeting the gC1qR-EGFR heterodimer receptor. This discovery offers a promising new therapeutic approach for the treatment of OPC.

Investigating the impact of the universal function of the nuclear proximity potential in heavy-ion fusion cross sections

The fusion barriers and cross sections of 15 colliding systems with 320 ≤ Z 1 Z 2 ≤ 1512 are investigated in detail to understand the influence of the universal function of proximity potential formalism in the heavy-ion fusion mechanism. To realize this goal, we select three versions of the phenomenological proximity potentials, including Prox. 77, Zhang 2013, and Guo 2013, to calculate the nucleus–nucleus potential. The experimental fusion cross sections for the selected reactions are analyzed using the standard coupled-channel calculations, including couplings to the low-lying 2+ and 3− states in the target and projectile. The calculated results show that the universal functions of the Guo 2013 and Prox. 77 models provide the lowest and highest fusion barriers, respectively. In addition, it is found that the height of the fusion barriers is enhanced by increasing the mass number of the projectile from light to heavy ones. The highest sensitivity to the mass number of the projectile belongs to the results of Prox. 77. A discussion is also presented on the influence of the universal function on the radial behavior of the interaction potential in the allowed region for overlapping configurations. Our results reveal that the best fit to the experimental data of the fusion cross sections for the reactions involving light and medium nuclei is obtained using the universal function of the Zhang 2013 model. For the heavier systems, the results of the Guo 2013 model at sub-barrier energies provide a good description of the available data.

Systematics of fusion of light nuclei

We have constructed the empirical formula for fusion barrier height (VB), fusion barrier position (RB), and inverted parabola (ħω) of light nuclei with atomic number in the range 2≤ZC≤10. This formula is obtained by studying the fusion barrier characteristics of 333 projectile target combinations. The values produced by the present formula are also compared with experiments. The present semi-empirical formula produces fusion barrier characteristics of light nuclei with the simple inputs of mass number (A) and atomic number (Z) of projectile targets. This semi-empirical formula can be utilized to calculate and interpret fusion barrier characteristics in light nuclear systems.

Tomosyns attenuate SNARE assembly and synaptic depression by binding to VAMP2-containing template complexes

Tomosyns are widely thought to attenuate membrane fusion by competing with synaptobrevin-2/VAMP2 for SNARE-complex assembly. Here, we present evidence against this scenario. In a novel mouse model, tomosyn-1/2 deficiency lowered the fusion barrier and enhanced the probability that synaptic vesicles fuse, resulting in stronger synapses with faster depression and slower recovery. While wild-type tomosyn-1m rescued these phenotypes, substitution of its SNARE motif with that of synaptobrevin-2/VAMP2 did not. Single-molecule force measurements indeed revealed that tomosyn’s SNARE motif cannot substitute synaptobrevin-2/VAMP2 to form template complexes with Munc18-1 and syntaxin-1, an essential intermediate for SNARE assembly. Instead, tomosyns extensively bind synaptobrevin-2/VAMP2-containing template complexes and prevent SNAP-25 association. Structure-function analyses indicate that the C-terminal polybasic region contributes to tomosyn’s inhibitory function. These results reveal that tomosyns regulate synaptic transmission by cooperating with synaptobrevin-2/VAMP2 to prevent SNAP-25 binding during SNARE assembly, thereby limiting initial synaptic strength and equalizing it during repetitive stimulation.

SNAP25 disease mutations change the energy landscape for synaptic exocytosis due to aberrant SNARE interactions.

SNAP25 is one of three neuronal SNAREs driving synaptic vesicle exocytosis. We studied three mutations in SNAP25 that cause epileptic encephalopathy: V48F, and D166Y in the synaptotagmin-1 (Syt1)-binding interface, and I67N, which destabilizes the SNARE complex. All three mutations reduced Syt1-dependent vesicle docking to SNARE-carrying liposomes and Ca2+-stimulated membrane fusion in vitro and when expressed in mouse hippocampal neurons. The V48F and D166Y mutants (with potency D166Y > V48F) led to reduced readily releasable pool (RRP) size, due to increased spontaneous (miniature Excitatory Postsynaptic Current, mEPSC) release and decreased priming rates. These mutations lowered the energy barrier for fusion and increased the release probability, which are gain-of-function features not found in Syt1 knockout (KO) neurons; normalized mEPSC release rates were higher (potency D166Y > V48F) than in the Syt1 KO. These mutations (potency D166Y > V48F) increased spontaneous association to partner SNAREs, resulting in unregulated membrane fusion. In contrast, the I67N mutant decreased mEPSC frequency and evoked EPSC amplitudes due to an increase in the height of the energy barrier for fusion, whereas the RRP size was unaffected. This could be partly compensated by positive charges lowering the energy barrier. Overall, pathogenic mutations in SNAP25 cause complex changes in the energy landscape for priming and fusion.

SNAP25 disease mutations change the energy landscape for synaptic exocytosis due to aberrant SNARE interactions

SNAP25 is one of three neuronal SNAREs driving synaptic vesicle exocytosis. We studied three mutations in SNAP25 that cause epileptic encephalopathy: V48F, and D166Y in the synaptotagmin-1 (Syt1)-binding interface, and I67N, which destabilizes the SNARE complex. All three mutations reduced Syt1-dependent vesicle docking to SNARE-carrying liposomes and Ca2+-stimulated membrane fusion in vitro and when expressed in mouse hippocampal neurons. The V48F and D166Y mutants (with potency D166Y > V48F) led to reduced readily releasable pool (RRP) size, due to increased spontaneous (miniature Excitatory Postsynaptic Current, mEPSC) release and decreased priming rates. These mutations lowered the energy barrier for fusion and increased the release probability, which are gain-of-function features not found in Syt1 knockout (KO) neurons; normalized mEPSC release rates were higher (potency D166Y > V48F) than in the Syt1 KO. These mutations (potency D166Y > V48F) increased spontaneous association to partner SNAREs, resulting in unregulated membrane fusion. In contrast, the I67N mutant decreased mEPSC frequency and evoked EPSC amplitudes due to an increase in the height of the energy barrier for fusion, whereas the RRP size was unaffected. This could be partly compensated by positive charges lowering the energy barrier. Overall, pathogenic mutations in SNAP25 cause complex changes in the energy landscape for priming and fusion.

Empirical model for fusion cross sections of Ca-induced reactions

A new empirical formula for the astrophysical S-factor has been suggested as a function of the Coulomb interaction parameter, center of mass energy, and barrier height. About 22 fusion reactions with 40,48Ca as projectiles were considered for different targets, leading to compound nuclei with atomic and mass numbers varying between 40 112 and , respectively. The fusion cross-sections have been estimated using the geometric factor, the Gamow-Sommerfield factor, and the empirical formula for the S-factor. This study's findings showed better agreement with those of available experiments when compared to Wong's formula. The present work leads to a smaller standard deviation value than Wong's formula when used to correlate the experimental data of calcium-induced fusion reactions. Wong's formula provides a good approximation of fusion cross-sections when the center of mass energy is below the fusion barrier when compared to above the fusion barrier.

Sub-barrier fusion dynamics in 28,30Si induced reactions with medium mass targets

The state-of-the-art technologies made it possible to reach the realms of fusion between two complex nuclei that offer an opportunity to explore a diverse spectrum of fusion phenomena. In this article, we have reported the influence of positive Q-value neutron transfer (PQNT) channels in fusion dynamics. Significant enhancement in sub-barrier fusion cross section has been observed for the 28Si+158Gd as compared to 30Si+140Ce and other similar systems with nearby mass asymmetry. Current findings include a comparison of the fusion excitation function of multiple systems on a reduced scale. The study sheds light on the influence of PQNT channels and deformation in nuclei on the sub-barrier fusion phenomenon. Further, fusion barrier parameters (barrier height and radius) extracted from the measured data demonstrate a good agreement with the empirical parameterization and proximity potential models.

Exploring the role of softness on the fusion dynamics of 58,64Ni+92,100Mo reactions

The structure of target and projectile nuclei can significantly affect the reaction dynamics at low energies. In the present work, the fusion mechanism of 58,64Ni+92,100Mo reactions involving the Mo isotopes exhibiting peculiar soft nature is explored within the relativistic mean-field (RMF) formalism. The cross-section for the considered reactions is obtained using the ℓ-summed Wong model furnished with nuclear interaction potential calculated within the self-consistent RMF formalism. The calculations are done for the two sets of RMF parameters, namely, NL3∗ and NL1, which give different values for various characteristics of nuclear matter at the saturation. A lower fusion barrier and consequently, a higher cross-section is obtained for the parameter set with comparatively softer equation of state (EoS). On comparing the theoretical cross-section with the available experimental data, an underestimation of fusion cross-section with respect to the experimental data at the sub-barrier energies is noted for the NL3∗ parametrizations. The match improves for the NL1 set having soft EoS with slight underestimation of data noted for all the considered reactions. These observations infer that the incomprehensible softness of Mo-isotopes also persists in their fusion dynamics, and the nuclear potential obtained within the RMF formalism is observed to underestimate the fusion probability for the reactions involving Mo-isotopes. The compressible nature of Mo-isotopes is inferred to enhance the fusion cross-section, and nuclear potential obtained for parameter set with soft EoS is observed to be more suitable for the description of their fusion dynamics.

Fusion dynamics of 12C + 46,48,50Ti reactions

Fusion dynamics of 12C + 46,48,50Ti reactions are examined by considering EDWSP and coupled channel (CC) formalism. The coupled channel outputs point out that there are significant contributions of the vibrational states of the Ti-isotopes and without taking into account of these states one cannot explain the behavior of the fusion outcomes of given reactions. The EDWSP based outputs govern barrier modifications and subsequently decreases effective fusion barrier between the participants. Because of it, EDWSP based computations consistently retrieve the fusion data of studied systems. Aforementioned models decently explored fusion behavior of given systems, which clearly reflects that barrier changing effects are appeared due to energy dependency in Woods-Saxon potential are quite similar to that of dominant channel couplings in CC approach.

Signatures of elongated and compact configurations in the fusion barrier distribution of deformed nuclei

The fusion barrier distributions (BD) of 11 fusion reactions are investigated to understand the role of orientation as a degree of freedom in the fusion mechanism involving deformed nuclei, and seeking signatures of cold and hot fusion. We compared the experimentally extracted BD with those calculated using the coupled-channel method, starting from orientation-dependent folding potentials based on M3Y-Reid nucleon–nucleon interaction, with coupling to the anticipated vibrational and rotational excitations in projectile and target nuclei. We found that the signature of the hot fusion process within the compact configuration of the participating deformed nuclei is always evident in the extracted fusion barrier distribution. The different peaks appearing in the extracted BD can be individually assigned to the elongated-cold or compact-hot fusion process. The imprint of the compact-hot fusion may also manifest itself as a little increase in the value of the BD at certain related energy, compared with the preceding and succeeding values.

Identification of Fangchinoline as a novel autophagy inhibitor with an adjuvant of chemotherapy against lung cancer

Autophagy is a fundamental recycling pathway that enhances cellular resilience, promoting survival. However, this survival mechanism can impede anti-cancer treatment strategies designed to induce cell death. In this study, we identified a novel autophagy inhibitor, Fangchinoline (Fan) isolated from the traditional Chinese medicine Stephania tetrandra. We speculated that when Fan blocks autophagy, cancer cells lose substantial self-preservation abilities during treatment. Firstly, we examined in detail the mechanism through which Fan inhibits autophagy. Specifically, Fan induced a significant increase in autophagosomes, as indicated by GFP-LC3 labeling, confirmed by the up-regulation of LC3-II. The autophagy receptor protein p62 was also up-regulated, suggesting a potential inhibition of autophagy flux. We further ruled out the possibility of fusion barriers between lysosomes and autophagosomes, as confirmed by their co-localization in double fluorescence staining. However, the lysosomal acid environment might be compromised, as suggested by the diminished fluorescence of acidity-sensitive dyes in the lysosomes and the corresponding decrease in mature forms of lysosomal cathepsin. To test the anti-cancer potential of Fan, we combined it with Cisplatin (Cis) or Paclitaxel (PTX) for lung cancer cell treatment. This combined treatment demonstrated a synergistically enhanced killing effect. These promising anti-tumor results were also replicated in a xenografted tumor model. The significance of this research lies in the identification of Fan as a potent autophagy inhibitor and its potential to enhance the efficacy of existing anti-cancer drugs. By unraveling the mechanisms of Fan's action on autophagy and demonstrating its synergistic effect in combination therapies, our study provides valuable insights for developing novel strategies to overcome autophagy-mediated resistance in cancer treatment.

The Effect of the Proton and Neutron as Probe for the Nuclear Fusion Reactions at Near-Barrier Energies

In this study, quantum mechanical calculations and a semi-classical approach were used to determine fusion the probability (Pfus), fusion barrier distribution (Dfus), and fusion cross section (σfus) for the systems 28Si + 90Zr, 28Si + 92Zr, 28Si + 94Zr, 41K + 28Si, and 45K + 28Si. The semiclassical approach involved the use of the WKB approximation to describe the relative motion between the projectile and target nuclei, and the Continuum Discretized Coupled Channel (CDCC) method of Alder-Winther (AW) to describe the intrinsic motion of the nuclei. The importance of the neutron and the proton transfer and exchange on the calculations of Pfus, Dfus, and σfus for the studied systems. The results showed that the consideration of the coupling-channel calculations for quantum mechanics and a semi-classical approach, are very important to be considered specifically around and below the Coulomb barrier. The results were compared with the measured data and found in reasonable agreement.

Fusion barrier distribution from measurement of quasielastic scattering at θ c.m. = 180°

Distribution of fusion barriers reveals the effect of structure of the collision partners on the dynamics of fusion between two heavy ions. Experimental barrier distribution can be extracted from precisely measured fusion excitation function. Quasielastic excitation function is related to fusion excitation function by conservation of incident flux. Hence, barrier distribution can also be extracted from quasielastic excitation function, which is usually measured at large angles, by detecting the back-scattered projectile-like ions. However, the reflectance coefficient is exactly complementary to the transmittance coefficient at θ c.m. = 180°, which corresponds to orbital angular momentum, ℓ = 0. We report here extraction of fusion barrier distribution for 16O+142 Ce from measurement of quasielastic scattering at θ c.m. = 180°, by detecting the target-like ions in the forward angles using a recoil mass spectrometer. Quasielastic excitation functions were also measured by detecting the projectile-like ions at two large angles. Barrier distributions extracted from both fusion and quasielastic measurements were found to be nearly identical. This work, thus, provided the first experimental verification of validity of the scaling property and the iso-centrifugal approximation in extracting barrier distribution from quasielastic excitation functions measured at large angles.

Influence of neutron transfer channels on fusion dynamics near the Coulomb barrier for 28Si + 116,120,124Sn systems

The phenomenon of enhanced fusion cross-section as compared to the theoretical predictions of 1-D BPM has been extensively studied over the past few decades. However, the unambiguous role of neutron transfer channels on the sub-barrier fusion enhancement is still elusive in most cases. Fusion cross-section measurements ≈ 15% below and above the Coulomb barrier were performed to elucidate the mechanisms responsible for the experimentally observed sub-barrier fusion enhancement. Coupled-channels calculations using CCFULL were used to decipher the reaction dynamics. CC calculations explained the fusion excitation function for 28Si + 116,120Sn systems after the inclusion of inelastic excitations along with a pair transfer. However, the observed behavior for the 28Si + 124Sn system could not be explained. The fusion barrier distribution has been extracted from the experimental data to unveil the various channels coupled in the concerned rection. A single uncoupled barrier was transformed into a distribution of barriers depicting the presence of different channels coupled in the reaction. The results indicate a significant effect from multi-neutron transfer channels on the fusion dynamics.

Investigation on the Quasifission hindrance to synthesis 298Og

Formation of a compound nucleus and production of its evaporation residue are hindered by quasi-fission process. It reduces the evaporation residue cross section since it takes place before the target and projectile combines to form a composite nucleus. We study the quasifission barriers (Bqf) for 14 fusion reactions in the formation of superheavy element 298Og within the framework of the di-nuclear system model. In particular, the influence of entrance channel parameters on quasifission barriers has been investigated. We notice that the quasifission barriers decreases with an increase in angular momentum and fusion barrier height. We constructed semi-empirical formulae for Bqf as a function of mean fissility. The fusion reaction 48Ca+250Cf poses larger Bqf. The larger evaporation cross section is observed for this fusion reaction for 3n evaporation channel with the cross-section of 0.81pb. Similarly, a smaller evaporation cross-section of about 0.033pb is observed for 51Cr+247Pu fusion reaction for 4n evaporation channel with both projectile and target being deformed, unlike to the previous reaction with spherical projectile and deformed target.