Hybrid discretizations of the Boltzmann equation for the dilute gas flow regime

New hybrid numerical model allows large scale flow simulations in high-tech production equipmen

DSMC-LBM mapping scheme for rarefied and non-rarefied gas flows

We present the formulation of a kinetic mapping scheme between the Direct Simulation Monte Carlo (DSMC) and the Lattice Boltzmann Method (LBM) which is at the basis of the hybrid model used to couple the two methods in view of efficiently and accurately simulate isothermal flows characterized by variable rarefaction effects. Owing to the kinetic nature of the LBM, the procedure we propose ensures to accurately couple DSMC and LBM at a larger Kn number than usually done in traditional hybrid DSMC-Navier-Stokes equation models. We show the main steps of the mapping algorithm and illustrate details of the implementation. Good agreement is found between the moments of the single particle distribution function as obtained from the mapping scheme and from independent LBM or DSMC simulations at the grid nodes where the coupling is imposed. We also show results on the application of the hybrid scheme based on a simpler mapping scheme for plane Poiseuille flow at finite Kn number. Potential gains in the computational efficiency assured by the application of the coupling scheme are estimated for the same flow.Comment: Submitted to Journal of Computational Scienc

Build up of yield stress fluids via chaotic emulsification

Stabilised dense emulsions display a rich phenomenology connecting microstructure and rheology. In this work, we study how an emulsion with a finite yield stress can be built via large-scale stirring. By gradually increasing the volume fraction of the dispersed minority phase, under the constant action of a stirring force, we are able to achieve a volume fraction close to (Formula presented.). Despite the fact that our system is highly concentrated and not yet turbulent we observe a droplet size distribution consistent with the (Formula presented.) scaling, often associated with inertial range droplets breakup. We report that the polydispersity of droplet sizes correlates with the dynamics of the emulsion formation process. Additionally, we quantify the visco-elastic properties of the dense emulsion finally obtained and we demonstrate the presence of a finite yield stress. The approach reported can pave the way to a quantitative understanding of the complex interplay between the dynamics of mesoscale constituents and the large-scale flow properties of yield stress fluids

Anatomical and functional changes after dexamethasone implant and ranibizumab in diabetic macular edema: A retrospective cohort study

AIM: To investigate the efficacy and safety of ranibizumab (RZB group) and dexamethasone implant (DEX group) intravitreal treatments in patients with treatment-na\uefve center involved diabetic macular edema (DME) by means of functional and morphological assessments. METHODS: This retrospective cohort study included 50 eyes of 50 patients with DME treated either with RBZ or DEX. Best-corrected visual acuity (BCVA) and microperimetry were evaluated at baseline and during a 6-month follow-up. In addition, central macular thickness (CMT) by means of structural optical coherence tomography (OCT) and retinal capillary plexus density and choriocapillary density by means of OCT angiography were assessed in all cases. RESULTS: Functional and morphological parameters significantly improved during the study period in both groups. BCVA improved significantly in both groups with a greater increase in the DEX group compared to the RBZ group (P=0.030). Microperimetry significantly differed during follow-up between the two treatments (P=0.031). In both groups CMT significantly decreased (P<0.001) without statistically significant differences between the two groups. A statistically significant increase of deep capillary plexus density was detected in both groups at 30d after therapy. The retreatment rate was 0.70\ub10.10 and 0.65\ub10.10 in the RBZ group and 0.65\ub10.10 and 0.50\ub10.11 in DEX group at 120 and 180d respectively. Two out of 25 patients in DEX group showed intraocular pressure increase requiring hypotonic eye drops. CONCLUSION: Both treatments are very effective for DME treatment during 6mo of follow-up with a lower retreatment rate in DEX group

Vascular risk factors in glaucoma: the results of a national survey

Background The role of vascular risk factors in glaucoma is still being debated. To assess the importance of vascular risk factors in patients with primary open-angle glaucoma (POAG), data from the medical history of 2,879 POAG patients and 973 age-matched controls were collected and analyzed. Methods Design: observational survey. Setting: 35 Italian academic centers. Study population: POAG patients and age-matched controls. In order to reduce bias consecutive patients were included. Observation procedures: data concerning vascular risk factors were collected for all patients with a detailed questionnaire. A complete ophthalmological examination with assessment of intraocular pressure (IOP), visual field, optic disc, and systemic blood pressure was performed. Main outcome measures: the ESH-ESC (European Society of Hypertension-European Society of Cardiology) guidelines were used to calculate the level of cardiovascular risk. Crude and adjusted estimates of the odds ratios (OR) were calculated for all cardiovascular risk factors in POAG and controls. Results The study included 2,879 POAG patients and 973 controls. POAG cases had a significantly higher systolic and diastolic blood pressure (p=0.001) and systolic perfusion pressure (p=0.02) as compared with controls. Also mean IOP was significantly higher in the POAG group (p=0.01), while diastolic perfusion pressure was not significantly different in the two groups. Myopia was more prevalent in the POAG group (23 vs 18%, p=0.005) as well as a positive family history for glaucoma (26 vs 12%, p= 0.004). POAG patients tended to have a higher cardiovascular risk than controls: 63% of glaucoma cases vs 55% of controls (OR: 1.38, p=0.005) had a “high” or “very high” cardiovascular risk. Conclusions The level of cardiovascular risk was significantly higher in glaucoma patients than in controls

Treatment of capecitabine corneal side effects with autologous blood-derived serum eye drops

Background/Aim: To describe the clinical progress and management of ocular side effects in a 35-yearold patient with metastatic breast cancer who underwent oral chemotherapy with capecitabine and lapatinib. Materials and Methods: Slit lamp evaluation revealed bilateral perikeratic hyperemia, perilimbal conjunctival edema associated with corneal marginal infiltrates and epithelial and anterior stromal defects in both eyes. Slit lamp examination, in vivo confocal microscopy and anteriorsegment optical coherence tomography were highly suggestive for limbal stem cell deficiency. The decision to administer autologous blood- derived serum eye drops was made. Results: Following administration of autologous blood-derived serum eye drops, corneal marginal infiltrates, epithelial and stromal defects significantly regressed in both eyes after only 10 days. Chemotherapy was resumed and serum eye drops were prescribed simultaneously. Conclusion: Autologous blood-derived serum eye drops may be an adequate therapeutic choice for bilateral corneal lesions detected as ocular side effects of capecitabine

Lattice Boltzmann accelerated direct simulation Monte Carlo for dilute gas flow simulations

Hybrid particle–continuum computational frameworks permit the simulation of gas flows by locally adjusting the resolution to the degree of non-equilibrium displayed by the flow in different regions of space and time. In this work, we present a new scheme that couples the direct simulation Monte Carlo (DSMC) with the lattice Boltzmann (LB) method in the limit of isothermal flows. The former handles strong non-equilibrium effects, as they typically occur in the vicinity of solid boundaries, whereas the latter is in charge of the bulk flow, where non-equilibrium can be dealt with perturbatively, i.e. according to Navier–Stokes hydrodynamics. The proposed concurrent multiscale method is applied to the dilute gas Couette flow, showing major computational gains when compared with the full DSMC scenarios. In addition, it is shown that the coupling with LB in the bulk flow can speed up the DSMC treatment of the Knudsen layer with respect to the full DSMC case. In other words, LB acts as a DSMC accelerator. This article is part of the themed issue ‘Multiscale modelling at the physics–chemistry–biology interface

Tectonic control on the deposition of the Lower Miocene sediments of the Monti della Maddalena Ridge (Southern Apennines): synsedimentary extensional deformation in a foreland setting

The Lower-Middle (?) Miocene deposits stratigraphically overly- ing the Meso-Cenozoic carbonate substratum in the Monti della Maddalena ridge (Southern Apennines) represent a pre-orogenic sedimentary cycle deposited in a foreland area that occupied the for- mer external margin of the Campano-Lucana Platform (CLP), before the tectonic emplacement of the Liguride accretionary wedge. A detailed stratigraphic and sedimentologic analysis has revealed that these deposits are characterized by strong vertical and lateral thick- ness and facies changes. These features are interpreted as the result of a complex basin geometry, consisting of asymmetric horst and graben structures bordered by steep fault planes. Thick calciclastic successions, made of breccia and turbidites, deposited in the down- thrown blocks, close to fault scarps, while the more distal areas are characterized by thinner and fine-grained successions. Condensed deposits are found on submerged structural highs. All the succes- sions show an overall thinning and fining upward trend and an evo- lution from calciclastic to siliciclastic deposits. Facies and stratigra- phy of the Lower-Middle (?) Miocene succession are best explained by a depositional setting strongly controlled by extensional tectonics related to flexural subsidence. The occurrence of lower Miocene deposits in neptunian dykes crosscutting the underlying carbonate succession strongly supports this hypothesis

Human amniotic membrane patch and platelet-rich plasma to promote retinal hole repair in a recurrent retinal detachment

Purpose: To present a modified surgical technique, based on a combination of human amniotic membrane (hAM) patch and autologous Platelet-rich plasma (PRP) in a case of recurrent retinal detachment (RRD) due to a perivascular retinal hole over an area of staphyloma in an eye with pathologic myopia. Methods: Presenting the surgical technique with the disposal of surgical video. After performing 23-gauge pars plana vitrectomy (PPV) the hAM patch was inserted under the neuroretina through the perivascular hole and PRP was injected on top to speed up the closure of the hole. To complete the surgical procedure High Viscosity Silicon oil (5000cst) was used as tamponade. The patient was prescribed to maintain a face-down position for the first 3 days after the operation. Follow-up was evaluated through Optical coherence tomography (OCT) scans. Results: The 3 days postoperative OCT showed a flat retina with the filling of the myopic staphyloma. The hAM patch was well positioned and the retinal hole could not be identified. At 6 weeks from intervention, the site of the retinal hole at OCT scan was covered by new tissue. Silicone oil was removed 3 months later with no recurrence. Conclusion: hAM transplantation is a novel technique in case of retinal detachment recurrences to seal retinal holes over high myopic chorioretinal atrophy. The adjunctive use of PRP and high viscosity silicon oil allows to reducing the standard face-down positioning timing, representing a valid solution for elderly patients who have difficulties maintaining the position for long periods