Soft Nuclei Research Articles

Chiral dynamics in soft triaxial nuclei

The chirality in soft triaxial nuclei is investigated for the first time with the time-dependent and tilted axis cranking covariant density functional theories on a three-dimensional space lattice in a microscopic and self-consistent way. Taking the puzzling chiral nucleus 106Ag as an example, the experimental energies of the observed nearly degenerate bands are well reproduced without any free parameters beyond the well-defined density functional. A novel chiral mode in soft triaxial nuclei is newly revealed from the microscopic dynamics of the total angular momentum. This opens a new research area for the study of chirality, particularly in relation to soft nuclear shapes.

Rotational technique for emulsification of soft lens nucleus

This study was conducted to develop a non-ultrasound technique for emulsification of a soft lens nucleus. Fifty-seven patients (57 eyes) underwent surgery. In 23 cases, early or immature cataracts were detected, and in 34 cases, lens removal was performed for refractive purposes in high myopia and complex myopic astigmatism. Phacoemulsifier Centurion Vision System (Alcon Laboratories, Inc., USA) was used for the surgery. Aspiration of soft lens nucleus was done using a rotational technique. The following aspects were evaluated in the course of the surgery: the volume of the required irrigation solution, and the frequency needing to involve ultrasound for complete emulsification of the lens nucleus. Intraoperative and postoperative complications were also assessed. The surgery was uneventful in all cases. There were no violations of the integrity of capsulorhexis edge. The need for short pulses of minimal power ultrasound during the removal of the soft lens using this technique arose only in 11 (19.3%) cases. The effective ultrasound time was less than 1 second. The required volume of irrigation solution was 33.0 (24.0; 43.0) ml, which does not differ significantly from that in ultrasonic phacoemulsification. The use of modern phacoemulsifiers providing a high vacuum level allows successful removal of a soft lens without using ultrasound, which prevents its negative impact on the ocular tissues. The use of adequate surgical techniques, including the optimal direction of rotation of the lens nucleus in the rotational technique, improves the efficiency of soft lens nucleus removal.

Surgical technique for aspiration of soft lens nucleus with preoperative femtosecond laser-assisted fragmentation

This study was conducted to develop a non-ultrasound technique for aspiration of a soft lens nucleus after its preliminary femtosecond laser-assisted fragmentation. The study included 63 patients (63 eyes) aged 23 to 40 years who underwent surgery. In 27 cases, early or immature cataract was observed, and in 36 cases, cataract removal was performed for refractive purposes in high myopia and complex myopic astigmatism. The VICTUS femtosecond laser surgical system (Technolas Perfect Vision GmbH, Germany) was used for preliminary fragmentation of the lens nucleus. Surgeries were performed using the Centurion Vision System phacoemulsifier (Alcon Laboratories, Inc., USA). The volume of the required irrigation solution was evaluated during the surgery. Intraoperative and postoperative complications were assessed. The surgery was performed without complications in all cases. Capsulorhexis edge was completely preserved along its entire circumference. The study showed the fundamental possibility of aspirating a cataract with a nucleus of grade I-II density without low-frequency ultrasound after preliminary femtosecond laser-assisted fragmentation of the nucleus with a "grid" pattern, which ensures minimal fragment size in the central zone of the nucleus. The volume of irrigation solution required for aspiration of the nucleus was 36.0 (27.0; 44.0) ml, which does not significantly differ from the volume of solution during ultrasound phacoemulsification of a nucleus of such density. Femtosecond laser-assisted fragmentation of the lens nucleus with a "grid" pattern and phacoemulsifier systems with a high vacuum level allow effective aspiration of a soft lens without using low-frequency ultrasound.

Comparisons of the clinical outcomes of Centurion® active fluidics system with a low IOP setting and gravity fluidics system with a normal IOP setting for cataract patients with low corneal endothelial cell density

BackgroundDuring cataract phacoemulsification surgery, the Alcon Centurion with Active Sentry can achieve a more stable anterior chamber, which allows a lower intraocular pressure (IOP) setting than the gravity fluidics system. In this randomized controlled trial, we compared these two systems’ damage to the cornea under different IOP settings.MethodsSeventy-eight eyes of 53 patients with corneal endothelial cell density (ECD) of 500∼1500/mm2 were enrolled and randomly divided into the active fluidics system (AFS) group using an Active Sentry handpiece with 30 mmHg IOP setting (40 eyes) and the gravity fluidics system (GFS) group using an Ozil handpiece with 80 cmH2O IOP setting (38 eyes). Intraoperative parameters, visual acuity, corneal edema ratio, central corneal thickness (CCT) changes as well as loss rate of ECD were analyzed.ResultsWe observed no significant differences in best corrected visual acuity (BCVA), cumulative dissipated energy (CDE), total case time, estimated fluidics usage (EFU) and ophthalmic viscoelastic devices (OVDs) usage between the two groups. The enrolled eyes were further divided into soft nucleus (27 eyes) and hard nucleus (51 eyes) subgroups. And we found less pain complaint during surgeries, lower corneal edema ratio at 1-day and 1-week visit, smaller CCT changes at 1-day visit and lower ECD loss rate at 1-month visit (p < 0.05) in both subgroups of the AFS group than in the GFS group, implying higher intraoperative comfort levels and less corneal damage of the AFS group with a low IOP setting.ConclusionOwing to a lower IOP setting, Centurion® Vision System with Active Sentry handpiece causes less corneal damage and pain perception during phacoemulsification for patients with low pre-operative ECD.Clinical Trial Registrationhttps://www.chictr.org.cn, identifier ChiCTR2300077865.

The Influence of Nucleus Mechanics in Modelling Adhesion-independent Cell Migration in Structured and Confined Environments

Recent biological experiments (Lämmermann et al. in Nature 453(7191):51–55, 2008; Reversat et al. in Nature 7813:582–585, 2020; Balzer et al. in ASEB J Off Publ Fed Am Soc Exp Biol 26(10):4045–4056, 2012) have shown that certain types of cells are able to move in structured and confined environments even without the activation of focal adhesion. Focusing on this particular phenomenon and based on previous works (Jankowiak et al. in Math Models Methods Appl Sci 30(03):513–537, 2020), we derive a novel two-dimensional mechanical model, which relies on the following physical ingredients: the asymmetrical renewal of the actin cortex supporting the membrane, resulting in a backward flow of material; the mechanical description of the nuclear membrane and the inner nuclear material; the microtubule network guiding nucleus location; the contact interactions between the cell and the external environment. The resulting fourth order system of partial differential equations is then solved numerically to conduct a study of the qualitative effects of the model parameters, mainly those governing the mechanical properties of the nucleus and the geometry of the confining structure. Coherently with biological observations, we find that cells characterized by a stiff nucleus are unable to migrate in channels that can be crossed by cells with a softer nucleus. Regarding the geometry, cell velocity and ability to migrate are influenced by the width of the channel and the wavelength of the external structure. Even though still preliminary, these results may be potentially useful in determining the physical limit of cell migration in confined environments and in designing scaffolds for tissue engineering.

Phase State, Surface Tension, Water Activity, and Accommodation Coefficient of Water-Organic Clusters Near the Critical Size for Atmospheric New Particle Formation.

Interactions between water and organic molecules in sub-4 nm clusters play a significant role in the formation and growth of secondary organic aerosol (SOA) particles. However, a complete understanding of the relevant water microphysics has not yet been achieved due to challenges in the experimental characterization of soft nuclei. Here, we use molecular dynamics simulations to study the phase-mixing states, surface tension, water activity, and water accommodation coefficient of organic-water clusters representative of freshly nucleated SOA particles. Our results reveal large deviations from the behavior expected based on continuum theories. In particular, the phase-mixing state has a strong dependence on cluster size; surface tension displays a minimum at a specific organic-water mass ratio (morg/mw ∼ 4.5 in this study) corresponding to a minimum inhibition of droplet nucleation associated with the Kelvin effect; and the water accommodation coefficient increases by a factor of 2 with nanocluster hygroscopic growth, in agreement with recent experimental studies. Overall, our results yield parametric relations for water microphysical properties in sub-4 nm clusters and provide insight into the role of water in the initial stages of SOA nucleation and growth.

Microscopic aspects of γ softness in atomic nuclei

One of the main research themes in quantum many-body systems is the emergence of collective features from microscopic degrees of freedom. Using the microscopic approach of the triaxial projected shell model, the authors demonstrate that admixing a few quasiparticle excitations into the vacuum configuration with a fixed triaxiality parameter $\ensuremath{\gamma}$ provides a quantitative description of the shape fluctuations of the $\ensuremath{\gamma}$-soft nucleus ${}^{104}$Ru. The collective features are elucidated using the quadrupole shape invariant analysis, and also the staggering phase classification of the $\ensuremath{\gamma}$ band.

The Impale Technique: An Approach for Softer Nuclei

We describe a novel cataract surgery technique that can be used for soft nuclei, which present difficulties for removal even for experienced surgeons. Such nuclei typically don't crack as easily, tend to break into fragments, and don't allow for full thickness segmentation after grooving.

X-Ray Reverberation Mapping of Ark 564 Using Gaussian Process Regression

Ark 564 is an extreme high-Eddington narrow-line Seyfert 1 galaxy, known for being one of the brightest, most rapidly variable soft X-ray active galactic nuclei (AGN), and for having one of the lowest temperature coronae. Here, we present a 410 ks NuSTAR observation and two 115 ks XMM-Newton observations of this unique source, which reveal a very strong, relativistically broadened iron line. We compute the Fourier-resolved time lags by first using Gaussian processes to interpolate the NuSTAR gaps, implementing the first employment of multitask learning for application in AGN timing. By simultaneously fitting the time lags and the flux spectra with the relativistic reverberation model reltrans, we constrain the mass at , although additional components are required to describe the prominent soft excess in this source. These results motivate future combinations of machine learning, Fourier-resolved timing, and the development of reverberation models.

Comparisons of the energy efficiency and intraocular safety of two torsional phacoemulsification tips

BackgroundDuring cataract phacoemulsification surgery, an Intrepid® balanced (IB) tip can achieve a larger amplitude, which may lead to higher energy efficiency than a Kelman (K) tip when paired with a torsional phaco platform. In this retrospective cohort study, we compared their energy efficiency and damage to the cornea under a new energy setting.MethodsThe medical records of 104 eyes of 79 patients were reviewed, with 47 eyes belonging to the IB group and 57 eyes belonging to the K group. All surgeries were performed on an Alcon Centurion® platform with gravity infiltration. Surgical parameters, visual outcome, central corneal thickness (CCT) changes, and endothelial cell density (ECD) loss rate were recorded and calculated.ResultsNo significant differences in postoperative best corrected visual acuity (BCVA), intraocular pressure (IOP), total ultrasound time, estimated fluid aspirated, CCT changes, or ECD loss rate were observed between the two groups. We divided the included eyes into soft nucleus and hard nucleus subgroups and found lower cumulative dissipated energy (CDE, 8.15 ± 8.02 vs 14.82 ± 14.16, P = 0.023), cumulative torsional energy (CTE, 8.06 ± 7.87 vs 14.13 ± 13.02, P = 0.027), and cumulative longitudinal energy (CLE, 0.09 ± 0.17 vs 0.69 ± 1.37, P = 0.017) in the IB group than in the K group, implying less energy used and higher energy efficiency of the IB tip.ConclusionLower CLE in the IB group indicates fewer phaco tip obstructions and a significantly higher capability to conquer hard nuclei with IB tips with statistical significance. With an ultra-perfusion cannula, the balanced tip does not cause more corneal damage.

A theoretical interpretation of the anomalous reduced E2 transition probabilities along the yrast line of neutron-deficient nuclei

The anomalous low-energy E2-related behavior of a triaxially deformed nuclei is examined within the framework of the interacting boson model. The results show striking features that include a B(E2;41+→21+)/B(E2;21+→01+)<1.0 transition rate and a E(41+)/E(21+)>2.0 excitation energy ratio that can be tracked back to a finite-N effect, which in a large-N limit of the theory yields normal results for a stable γ-deformation. This description is shown to explain experimentally observed results in 172Pt and 168Os, and in doing so yields a deeper understanding of the physical features of a soft triaxially-deformed nucleus.

"Stop & drop"- a modified "stop & chop" phacoemulsification technique for cataract surgery.

To introduce a novel technique termed "stop and drop" for creating the first crack in the initial hemi-nucleus, eliminating the need to slip a chopper under the anterior capsular rim during horizontal chopping, hence lowering the risk of capsular or zonular damage. Placing a blunt chopper tip on the upper surface of the hemisection proximal to the capsular edge and pressing it downward to initiate a crack in a pinching manoeuvre. Once a crack has formed, the chopper can slide to the side, widening the crack and assisting the phaco needle to pull out the first fragment. The technique was used in over 100 cases of cataracts successfully. No radial tear, posterior capsule rupture or zonulolysis occurred. "Stop and drop" is an effective and safe technique for performing phacoemulsification. It is not suitable for soft nuclei where the chopper will likely "cheese-wire" through the nuclear material.

Questioning the wobbling interpretation of low-spin bands in γ -soft nuclei within the interacting boson-fermion model

An alternative interpretation of the recently reported low-lying excited bands in $\gamma$-soft odd-mass nuclei as wobbling bands is presented in terms of the interacting boson-fermion model. The model Hamiltonian is determined based on the mean-field calculations with the nuclear energy density functionals. The predicted mixing ratios of the $\Delta{I}=1$ electric quadrupole to magnetic dipole transition rates between yrast bands and those yrare bands previously interpreted as wobbling bands in $^{135}$Pr, $^{133}$La, $^{127}$Xe, and $^{105}$Pd are consistently smaller in magnitude than the experimental values on which the wobbling interpretation is based. These calculated mixing ratios indicate predominant magnetic character in agreement with the new experimental data. The earlier wobbling assignments are severely questioned.

Viscous shaping of the compliant cell nucleus.

The cell nucleus is commonly considered to be a stiff organelle that mechanically resists changes in shape, and this resistance is thought to limit the ability of cells to migrate through pores or spread on surfaces. Generation of stresses on the cell nucleus during migration and nuclear response to these stresses is fundamental to cell migration and mechano-transduction. In this Perspective, we discuss our previous experimental and computational evidence that supports a dynamic model, in which the soft nucleus is irreversibly shaped by viscous stresses generated by the motion of cell boundaries and transmitted through the intervening cytoskeletal network. While the nucleus is commonly modeled as a stiff elastic body, we review how nuclear shape changes on the timescale of migration can be explained by simple geometric constraints of constant nuclear volume and constant surface area of the nuclear lamina. Because the lamina surface area is in excess of that of a sphere of the same volume, these constraints permit dynamic transitions between a wide range of shapes during spreading and migration. The excess surface area allows the nuclear shape changes to mirror those of the cell with little mechanical resistance. Thus, the nucleus can be easily shaped by the moving cell boundaries over a wide range of shape changes and only becomes stiff to more extreme deformations that would require the lamina to stretch or the volume to compress. This model explains how nuclei can easily flatten on surfaces during cell spreading or elongate as cells move through pores until the lamina smooths out and becomes tense.

EphA2 Affects Development of the Eye Lens Nucleus and the Gradient of Refractive Index.

PurposeOur studies in mouse eye lenses demonstrate that ephrin-A5 and EphA2 are needed for normal epithelial cells and lens transparency. We sought to determine whether EphA2 and ephrin-A5 are important for lens morphometrics, nucleus formation, and refractive index.MethodsWe performed tissue morphometric measurements, electron microscopy, Western blots, and interferometric measurements using an X-ray synchrotron beam source to measure the gradient of refractive index (GRIN) to compare mouse lenses with genetic disruption of EphA2 or ephrin-A5.ResultsMorphometric analysis revealed that although there is no change in the overall lens volume, there is a change in lens shape in both EphA2−/− lenses and ephrin-A5−/− lenses. Surprisingly, EphA2−/− lenses had small and soft lens nuclei different from hard lens nuclei of control lenses. SEM images revealed changes in cell morphology of EphA2−/− fiber cells close to the center of the lens. Inner EphA2−/− lens fibers had more pronounced tongue-and-groove interdigitations and formed globular membrane morphology only in the deepest layers of the lens nucleus. We did not observe nuclear defects in ephrin-A5−/− lenses. There was an overall decrease in magnitude of refractive index across EphA2−/− lenses, which is most pronounced in the nucleus.ConclusionsThis work reveals that Eph-ephrin signaling plays a role in fiber cell maturation, nuclear compaction, and lens shape. Loss of EphA2 disrupts the nuclear compaction resulting in a small lens nucleus. Our data suggest that Eph-ephrin signaling may be required for fiber cell membrane reorganization and compaction and for establishing a normal GRIN.

Interplay between pairing and triaxial shape degrees of freedom in Os and Pt nuclei

The effect of coupling between pairing and quadrupole triaxial shape vibrations on the low-energy collective states of $\gamma$-soft nuclei is investigated using a model based on the framework of nuclear energy density functionals (EDFs). Employing a constrained self-consistent mean-field (SCMF) method that uses universal EDFs and pairing interactions, potential energy surfaces of characteristic $\gamma$-soft Os and Pt nuclei with $A\approx190$ are calculated as functions of the pairing and triaxial quadrupole deformations. Collective spectroscopic properties are computed using a number-nonconserving interacting boson model (IBM) Hamiltonian, with parameters determined by mapping the SCMF energy surface onto the expectation value of the Hamiltonian in the boson condensate state. It is shown that, by simultaneously considering both the shape and pairing collective degrees of freedom, the EDF-based IBM successfully reproduces data on collective structures based on low-energy $0^{+}$ states, as well as $\gamma$-vibrational bands.

Triaxiality in the mid-shell nucleus Pd112

Lifetimes of low-spin excited states in $^{112}\mathrm{Pd}$ were measured using the recoil-distance Doppler-shift technique. The nucleus of interest was populated in a $^{110}\mathrm{Pd}(^{18}\mathrm{O},^{16}\mathrm{O})^{112}\mathrm{Pd}$ reaction using the Cologne FN Tandem accelerator. Three lifetimes of ground-state band members and one lifetime of the $\ensuremath{\gamma}$ band were measured. From these lifetimes reduced transition probabilities were extracted and compared to interacting boson model, $\ensuremath{\gamma}$-soft calculations, and Davydov calculations. The lifetime of the ${2}_{\ensuremath{\gamma}}^{+}$ gives some insights on the nuclear shape and structure of the $\ensuremath{\gamma}$ band. The deduced transition rates show an indicator for a rigid triaxial nucleus as well as more indicators for a $\ensuremath{\gamma}$-soft nucleus.

Coupling of pairing and triaxial shape vibrations in collective states of γ -soft nuclei

In addition to shape oscillations, low-energy excitation spectra of deformed nuclei are also influenced by pairing vibrations. The simultaneous description of these collective modes and their coupling has been a long-standing problem in nuclear structure theory. Here we address the problem in terms of self-consistent mean-field calculations of collective deformation energy surfaces, and the framework of the interacting boson approximation. In addition to quadrupole shape vibrations and rotations, the explicit coupling to pairing vibrations is taken into account by a boson-number non-conserving Hamiltonian, specified by a choice of a universal density functional and pairing interaction. An illustrative calculation for $^{128}$Xe and $^{130}$Xe shows the importance of dynamical pairing degrees of freedom, especially for structures built on low-energy $0^+$ excited states, in $\gamma$-soft and triaxial nuclei.

Crucial Role of Lamin A/C in the Migration and Differentiation of MSCs in Bone.

Lamin A/C, intermediate filament proteins from the nuclear lamina encoded by the LMNA gene, play a central role in mediating the mechanosignaling of cytoskeletal forces into nucleus. In fact, this mechanotransduction process is essential to ensure the proper functioning of other tasks also mediated by lamin A/C: the structural support of the nucleus and the regulation of gene expression. In this way, lamin A/C is fundamental for the migration and differentiation of mesenchymal stem cells (MSCs), the progenitors of osteoblasts, thus affecting bone homeostasis. Bone formation is a complex process regulated by chemical and mechanical cues, coming from the surrounding extracellular matrix. MSCs respond to signals modulating the expression levels of lamin A/C, and therefore, adapting their nuclear shape and stiffness. To promote cell migration, MSCs need soft nuclei with low lamin A content. Conversely, during osteogenic differentiation, lamin A/C levels are known to be increased. Several LMNA mutations present a negative impact in the migration and osteogenesis of MSCs, affecting bone tissue homeostasis and leading to pathological conditions. This review aims to describe these concepts by discussing the latest state-of-the-art in this exciting area, focusing on the relationship between lamin A/C in MSCs’ function and bone tissue from both, health and pathological points of view.

Comparison of Perioperative Parameters in Femtosecond Laser-Assisted Cataract Surgery Using 3 Nuclear Fragmentation Patterns

The purpose of this study was to compare the perioperative parameters of quadrant, sextant, and grid lens fragmentation patterns in femtosecond laser-assisted cataract surgery (FLACS). Prospective randomized clinical trial. Setting: Eye Center of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China. A total of 894 eyes in 661 patients with cataracts were enrolled. Intervention or observation procedures: the nuclear density was graded according to the Emery-Little classification. Patients received lens fragmentation using a quadrant, sextant, or grid pattern after random allocation. Evaluations included intraoperative parameters, complications, and postoperative outcomes. effective phacoemulsification time (EPT), intraoperative complications, visual acuity and intraocular pressure at one day postoperatively, as well as endothelial cell density, endothelial cell loss, and central corneal thickness at 1week postoperatively. In grade 1 nuclei, the mean EPT in the grid group was the shortest compared to those in the quadrant (P= 0.011) and sextant (P= 0.001) groups. In grade 2 nuclei, all 3 patterns showed no significant differences in the mean EPT (P > 0.05). In grade 3 nuclei, the sextant group revealed shorter mean EPT than the grid (P= 0.017) and quadrant (P > 0.05) groups. In grades 4 and 5 nuclei, the quadrant pattern had the shortest mean EPT among all 3 patterns (P < 0.05). The grid pattern is associated with higher intraocular pressure in hard nuclei (grades 4 and 5) than the other 2 patterns (P < 0.05). The grid and quadrant patterns allow for shorter EPT in soft (grade 1) and hard (grades 4 and 5) nuclei, respectively. All 3 patterns can be selected for treating grade 2 nuclei. The sextant pattern may be the best option when treating grade 3 nuclei. The grid pattern should be avoided in hard nuclei combined with glaucoma or glaucoma suspect.