3-month post-procedural evaluation of a combined intense pulsed light and photo-biomodulation system in the treatment of meibomian gland dysfunction.

PURPOSE: Meibomian gland dysfunction (MGD) is the leading cause of dry eye syndrome. It is a frequent and underdiagnosed condition with a significant socioeconomic impact. We propose here the evaluation of a platform combining intense pulsed light and photo-biomodulation in the treatment of Meibomian gland dysfunction. METHODS: We conducted a retrospective study at Brest University Hospital analyzing a cohort of 74 eyes (37 patients) at 1 month and 3 months after a protocol of 3 Eye-Light® (Espansione Group, Italy) sessions 14 days apart between January 2019 and April 2020. The primary outcome was the change in OSDI quality of life score. Secondary outcomes were the SPEED questionnaire score; tear break-up time (BUT), Oxford score, non-invasive break-up time (NIBUT), lipid layer thickness, lacrimal meniscus height and Meibomian gland atrophy rate. Tolerance of the treatment was also evaluated. RESULTS: We found a significant improvement in OSDI scores at 1 month (-17.32; 95% CI (-25.84; -8.79), P<0.0001) and 3 months (-16.95; 95% CI (-25.26; -8.64), P<0.0001). The SPEED score, BUT, Oxford score, Meibomian gland atrophy and NIBUT were also statistically significantly improved. Tolerance to treatment was very good despite two cases of herpetic keratitis, which resolved on treatment. CONCLUSION: Treatment with the Eye-Light® in three sessions every two weeks significantly reduced symptoms and ocular surface damage in patients with MGD. This data suggests that the use of Eye-Light® may represent a good option for patients with MGD.

Prediction of superconductivity in Li, K, Ca, and Sr-intercalated blue phosphorene bilayer using first-principle calculations.

Blue phosphorene is an interesting two-dimensional (2D) material, which has attracted the attention of researchers, due to its affluent physical and chemical properties. In recent years, it was discovered that the intercalation of alkali metals and alkaline earth metals in 2D materials may lead to conventional Bardeen-Cooper-Schrieffer (BCS) superconductivity. In this work, the electronic structure, phonon dispersion, Eliashberg spectral function, electron-phonon coupling (EPC), and the critical temperature of blue phosphorene bilayer intercalated by alkali metals (Li, and K) and alkaline earth metals (Ca, and Sr) for both AB and AC stacking orders are studied using the density functional theory and the density functional perturbation theory, within the generalized gradient approximation with van der Waals correction. The present work shows that the blue phosphorene bilayer is dynamically stable in AB stacking for Li and AC stacking for K, Ca, and Sr, and after intercalation, it transforms from a semiconductor to a metal owing to charge transfer between intercalated atoms and phosphorene. Furthermore, the EPC constant and the critical temperature are higher than those of 2D BCS-type superconductors. They are about 3 and 24.61 K respectively for K-intercalated blue phosphorene bilayer. Thus, our results suggest that blue phosphorene is a good candidate for a superconductor.

Theoretical investigation of FAPbSnGeX3 efficiency.

The use of hybrid lead halide perovskites as light absorbers in photovoltaic cells have gained large interest due to their optoelectronic properties and high efficiency. However, most hybrid perovskites contain toxic lead which has a negative impact on the environment. In this work, we systematically study the structural, electronic, and optical properties of lower lead halide perovskites FAPb0.5Sn0.25Ge0.25X3 (X = I, Br, Cl), as well as discussing their photovoltaic performance (open circuit voltage (V oc), the short circuit current density (J sc), and the power conversion efficiency (η)) using density functional theory (DFT), and we compare these with FAPbX3 (X = I, Br, Cl) frameworks. The compounds show a suitable band gap for photovoltaic applications, in which iodine has a lower gap value compared to chlorine. It is noteworthy that we found that lead doping by both germanium and tin in the FAPb0.5Sn0.25Ge0.25X3 (X = I, Br, Cl) materials significantly improves the adsorption coefficient and the stability of these systems compared to the FAPbX3 (X = I, Br, Cl) systems. The calculated Jsc shows a monotonical decrease from FAPb0.5Sn0.25Ge0.25I3 to FAPbCl3, which represents the lowest Jsc. Results reveal that FAPb0.5Sn0.25Ge0.25Cl3 demonstrates promising potential for photovoltaic application as it shows the highest efficiency. This study can help reduce the toxicity of hybrid lead halide perovskites and also raises their experimental power conversion efficiency.

First-principles study of closo-dodecaborates M2B12H12 (M = Li, Na, K) as solid-state electrolyte materials.

Closo-dodecaborates M2B12H12 are considered among the potential candidates for solid-state electrolyte materials due to their high ionic conductivities. It has been demonstrated that the reorientation of the icosahedral anion B12H122- plays a key role in high cation motion. However, this category of BnHn materials is still not well established with respect to their structural, thermodynamic and diffusion properties. In the present work, the electronic, vibrational and thermodynamic properties of M2B12H12 (M = Li, Na, K) structures are reported using first-principles calculations. The results of structural and electronic properties show that these structures have an insulator character with a large band gap of 5.75, 5.63 and 5.59 eV, respectively, for Li2B12H12, Na2B12H12 and K2B12H12. The thermodynamic stabilities of these systems are confirmed by their phonon calculation results. The primary quantities, such as heat capacity, vibrational entropy and volume variation at finite temperatures, are determined using the quasi-harmonic approximation in order to provide an input for the Gibbs free energy assessment. The calculated enthalpy of formation of the Li2B12H12 structure at 0 K and the proposed one at 300 K are found to be -127.31 and -740.44 kJ mol-1 per H2, respectively. The migration energy barrier of various cations in each system is calculated to be 0.7 (Li+), 1.16 (Na+) and 1.25 eV (K+), where the lowest energy barrier corresponds to the lithium ion migration in Li2B12H12. Additionally, the molecular dynamics simulation of M2B12H12 (M = Li, Na, K) structures demonstrated that these structures are stable above room temperature, except for the Li2B12H12 structure at 600 K, where the most stable is Na2B12H12. Finally, the temperature effect on icosahedral anion reorientation in each structure is elucidated as a function of temperature and cation type.

Shear thinning and shear thickening of a confined suspension of vesicles.

Widely regarded as an interesting model system for studying flow properties of blood, vesicles are closed membranes of phospholipids that mimic the cytoplasmic membranes of red blood cells. In this study we analyze the rheology of a suspension of vesicles in a confined geometry: the suspension, bound by two planar rigid walls on each side, is subject to a shear flow. Flow properties are then analyzed as a function of shear rate γ[over ̇], the concentration of the suspension ϕ, and the viscosity contrast λ=η_{in}/η_{out}, where η_{in} and η_{out} are the fluid viscosities of the inner and outer fluids, respectively. We find that the apparent (or effective viscosity) of the suspension exhibits both shear thinning (decreasing viscosity with shear rate) or shear thickening (increasing viscosity with shear rate) in the same concentration range. The shear thinning or thickening behaviors appear as subtle phenomena, dependant on viscosity contrast λ. We provide physical arguments on the origins of these behaviors.

Boltzmann equations and ab initio calculations: comparative study of cubic and wurtzite CdSe.

The electronic and optical properties of CdSe in two phases, cubic and wurtzite, have been studied by first principal calculations using the density functional theory. The optical parameters such as transmittance, optical absorption, refractive index and extinction coefficient have been investigated. We have calculated also the band structure, and total/partial density of state using the full potential-linearized augmented plane wave method with the local density approximation, generalized gradient approximation and the modified Becke-Johnson functional (mBJ), implemented in the Wien2k package. With the mBJ approximation the gap found for cubic and wurtzite structure is direct and is equal to 1.85 and 1.7 eV respectively, what corresponds to the experiment results. The optical absorption is significant in the ultraviolet field while it becomes low beyond 600 nm in the visible light for CdSe in different structures. From λ = 400 nm the transmittance is stable and reaches 80 %. With Boltztrap package, we have investigated also that with increasing temperature, the electrical conductivity increases. During the calculation, the cubic structure has presented an isotropy. While for wurtzite CdSe, the propagation of waves into system is different in xx and zz directions. These results can be exploited in several applications of CdSe in optoelectronic devices.

The plasma protein fibrinogen stabilizes clusters of red blood cells in microcapillary flows.

The supply of oxygen and nutrients and the disposal of metabolic waste in the organs depend strongly on how blood, especially red blood cells, flow through the microvascular network. Macromolecular plasma proteins such as fibrinogen cause red blood cells to form large aggregates, called rouleaux, which are usually assumed to be disaggregated in the circulation due to the shear forces present in bulk flow. This leads to the assumption that rouleaux formation is only relevant in the venule network and in arterioles at low shear rates or stasis. Thanks to an excellent agreement between combined experimental and numerical approaches, we show that despite the large shear rates present in microcapillaries, the presence of either fibrinogen or the synthetic polymer dextran leads to an enhanced formation of robust clusters of red blood cells, even at haematocrits as low as 1%. Robust aggregates are shown to exist in microcapillaries even for fibrinogen concentrations within the healthy physiological range. These persistent aggregates should strongly affect cell distribution and blood perfusion in the microvasculature, with putative implications for blood disorders even within apparently asymptomatic subjects.

On the problem of slipper shapes of red blood cells in the microvasculature.

Red blood cells (RBC) are known to exhibit non symmetric (slipper) shapes in the microvasculature. Vesicles have been recently used as a model for RBC and numerical simulations proved the existence of slipper shapes under Poiseuille flow (both in unconfined and confined geometry). However, in our recent numerical simulations the transition from symmetric (parachute) shape to the slipper one was found to take place upon decreasing the flow strength, while experiments on RBCs showed the contrary. In this work we show that if the viscosity contrast (ratio between the internal over external fluid viscosities) is different from unity, as is the case with RBCs, the transition from parachute to slipper shape occurs upon increasing the flow strength, in agreement with experiments. We provide the phase diagram of shapes in the microcirculation. The slipper is found to have a higher speed than the parachute (for the same parameters), that we believe to be the basic reason for its prevailing in the microvasculature. We provide a simple geometrical picture that explains the slipper flow efficiency over the parachute one. Finally, we show that there exists in parameter space regions of co-existence of slipper/parachute shapes and suggest simple experimental protocols to test these findings. The coexistence of shapes seems to be supported by experiments, though a systematic experimental study is lacking. A potential application of this work is to guide designing flow-based experiments in order to link the shape of RBCs to pathologies affecting cell deformability, such as sickle cell diseases, malaria, and those affecting blood hematocrit, as in polycythemia vera disease.

Complexity of vesicle microcirculation.

This study focuses numerically on dynamics in two dimensions of vesicles in microcirculation. The method used is based on boundary integral formulation. This study is inspired by the behavior of red blood cells (RBCs) in the microvasculature. Red RBCs carry oxygen from the lungs and deliver it through the microvasculature. The shape adopted by RBCs can affect blood flow and influence oxygen delivery. Our simulation using vesicles (a simple model for RBC) reveals unexpected complexity as compared to the case where a purely unbounded Poiseuille flow is considered [Kaoui, Biros, and Misbah, Phys. Rev. Lett. 103, 188101 (2009)]. In sufficiently large channels (in the range of 100 µm; the vesicle size and its reduced volume are taken in the range of those of a human RBC), such as arterioles, a slipperlike (asymmetric) shape prevails. A parachutelike (symmetric) shape is adopted in smaller channels (in the range of 20 µm, as in venules), but this shape loses stability and again changes to a pronounced slipperlike morphology in channels having a size typical of capillaries (5-10 µm). Stiff membranes, mimicking malaria infection, for example, adopt a centered or off-centered snakelike locomotion instead (the denomination snaking is used for this regime). A general scenario of how and why vesicles adopt their morphologies and dynamics among several distinct possibilities is provided. This finding potentially points to nontrivial RBCs dynamics in the microvasculature.

Rheology of particulate suspensions in a Poiseuille flow.

Particulate dense suspensions behave as complex fluids. They do not lend themselves easily to analytical solution. We propose an analytical model to mimic this problem. Namely, we consider arrays of long parallel plates which represent a simplification of arrays of chains of spherical particles. This simplified model can be solved analytically. The effect of effective rotation of the spherical particles is taken into account by attributing different velocities on each side of the plate that mimics the fact that particles are subject to shear. This work is an extension of a previous study where particle rotation was disregarded. The flow rate, the dissipation and the apparent viscosity are studied as a function of the underlying structure. For a single plate placed out of the flow center, the viscosity is lower when rotation is taken into account. For two plates, the minimal viscosity corresponds to the situation where the particles are as close as possible to the center and arranged symmetrically with respect to the center. We compute the rheological properties for arbitrary plate positions, and exploit them for a periodic arrangement. For N plates, and in a confined geometry, the viscosity is about twice as small as compared to the situation where rotation is ignored. We have conducted a numerical study of a suspension of spherical particles, and linear chains of spherical particles. The numerical study is in good qualitative and semiquantitative agreement with the analytical theory considering long plates. This agreement highlights the fact that our analytical model captures the essential features of a real suspension. The numerical study is based on a fluid dynamic particle method where the particles are represented by a scalar field having high viscosity inside.

Laparoscopic promontory sacral colpopexy: is the posterior, recto-vaginal, mesh mandatory?

OBJECTIVE(S): The aim of our retrospective study was to determine if systematic placement of a posterior mesh, in addition to an anterior vesico-vaginal mesh, is necessary for laparoscopic treatment of pelvic organ prolapse. METHODS: A laparoscopic promontory sacral colpopexy was performed in 108 patients, including 55 patients with a concurrent laparoscopic Burch procedure (50.9%). We compared 33 patients treated with a single anterior mesh (SAM) and 71 treated with a double, anterior and posterior, mesh (DM). RESULTS: The difference between the SAM and DM groups was statistically significant in terms of posterior compartment failure (rectocele and/or enterocele): 31.3% and 5.9%, respectively (p=0.0006). This significant difference persisted in the Burch (B) group (p=0.001), but not in the non-Burch (NB) group (p=0.98). Among the SAM group, this difference between the B and NB groups, was significant (57.1% versus 0%; p=0.0015) and above all not a single posterior failure was observed in the NB group. CONCLUSION(S): The placement of a posterior mesh, if highly effective, appeared unnecessary in the absence of an associated Burch procedure or a patent posterior prolapse. The posterior mesh also increased risk of postoperative complications and side effects.

Anisotropy effect on two-dimensional cellular-automaton traffic flow with periodic and open boundaries.

Using computer simulations we investigate, in a version of the Biham-Middleton-Levine model with random sequential update on a square lattice, the anisotropy effect of the probabilities of the change of the motion directions of cars, from up to right (p(ur)) and from right to up (p(ru)), on the dynamical jamming transition and velocities under periodic boundaries on one hand and the phase diagram under open boundaries on the other hand. However, in the former case, the sharp jamming transition appears only for p(ur)=0=p(ru)=0 (i.e., when the cars alter their motion directions). In the open boundary conditions, it is found that the first-order line transition between jamming and moving phases is curved. Hence, by increasing the anisotropy, the moving phase region expands as well as the contraction of the jamming and maximal current phases takes place. Moreover, in the anisotropic case, the transition between the jamming phase (or moving phase) and the maximal current phase is of second order while in the isotropic case, and when each car changes its direction of motion at every time step (p(ru)=p(ur)=1), the transition is of first order. Furthermore, in the maximal current phase, the density profile decays with an exponent gamma approximately 1/4.

Complete solo laparoscopic radical prostatectomy: initial experience.

OBJECTIVES: To demonstrate the feasibility of "complete solo" (CS) laparoscopic radical prostatectomy (LRP) performed solely with robotic manipulation of the laparoscope and without any human assistant at all. A comparison was made between CS LRP and the standard technique to identify the advantages and drawbacks. METHODS: Sixteen consecutive patients undergoing CS LRP were compared with the last 16 patients undergoing standard LRP. The standard procedure was performed with five trocars and one human assistant. Therefore, the surgeon had three instruments immediately available and could switch quickly from one to another, while the assistant held the laparoscope and a retractor. The CS method used a voice-controlled robotic arm to manipulate the laparoscope and a mechanical arm for the assisting instrument. RESULTS: The mean operative time in the CS and standard groups was 324 and 347 minutes, respectively (P >0.5). An additional human assistant was required, for 1 hour, in 3 patients of each group. No significant difference was noted between the two groups in terms of catheterization time, hospital stay, positive margin rate, complications, short-term cancer control, or functional results. The CS method has been demonstrated to be highly cost-effective compared with the standard technique. CONCLUSIONS: The CS LRP is feasible and compares favorably with the standard technique. It offers unique advantages in terms of direct control of the operative view, standardization of the assistance, and higher stability of the laparoscope, thus greatly enhancing the surgeon's comfort. The diminished need for human operative assistance provides significant economic and organizational benefits.

Continuously varying critical exponents in a sandpile model with internal disorder.

A sandpile model with an internal disorder is presented. The updating of critical sites is done according to a stochastic rule (with a probabilistic toppling q). Using a unified mean-field theory and numerical simulations, we have shown that the criticality is ensured for any value of q. The static critical exponents have been calculated and found to be the same as those obtained for the deterministic sandpile model, which is a particular case of the stochastic model. They have a universal q-independent behavior. In the limit of slow driving, we have developed a relation between our model and the branching process in order to compute the size exponent tau. It presents a continuous variation with the parameter of toppling q.

Edge wetting of an Ising three-dimensional system.

The effect of edge on wetting and layering transitions of a three-dimensional spin-1/2 Ising model is investigated, in the presence of longitudinal and surface magnetic fields, using mean field theory and Monte Carlo simulations. For T=0, the ground state phase diagram shows that there exist only three allowed transitions, namely, surface and bulk transition, surface transition, and bulk transition. However, there exist a surface intralayering temperature T(s)(L), above which the surface and the intralayering surface transitions occur. While the bulk layering and intralayering transitions appear above another finite temperature T(b)(L)(>or=T(s)(L)). These surface and bulk intralayering transitions are not seen in the perfect surfaces case. Numerical values of T(s)(L) and T(b)(L), computed by Monte Carlo method are found to be smaller than those obtained using mean field theory. However, the results predicted by the two methods become similar, and are exactly those given by the ground state phase diagram, for very low temperatures. On the other hand, the behavior of the local magnetizations as a function of the external magnetic field, shows that the transitions are of the first order type. T(s)(L) and T(b)(L) decrease when increasing the system size and/or the surface magnetic field. In particular, T(b)(L) reaches the wetting temperature T(w) for sufficiently large system sizes.

Kinetic Ashkin-Teller model with competing dynamics.

We study a two-dimensional nonequilibrium Ashkin-Teller model based on competing dynamics induced by contact with a heat bath at temperature T, and subject to an external source of energy. The dynamics of the system is simulated by two competing stochastic processes: a Glauber dynamics with probability p, which simulates the contact with the heat bath; and a Kawasaki dynamics with probability 1-p, which takes into account the flux of energy into the system. Monte Carlo simulations were employed to determine the phase diagram for the stationary states of the model and the corresponding critical exponents. The phase diagrams of the model exhibit a self-organization phenomenon for certain values of the fourth coupling interaction strength. On the other hand, from exponent calculations, the equilibrium critical behavior is preserved when nonequilibrium conditions are applied.