Alternative derivation of mean-field equations for composite fermions

La hamiltoniana que describe fermiones compuestos es presentada usualmente en forma fenomenológica, conociendo de antemano la forma funcional que se espera para describir tal sistema. En este trabajo, utilizando una lagrangiana de gauge no relativista U(1) × U(1) de electrones en un campo electromagnético, mostramos cómo obtener la hamiltoniana de campo medio que describe fermiones compuestos en 2+1 dimensiones en forma rigurosa. Además, comparamos estos resultados con los que obtenemos al considerar la inclusión de un término de masa topológica para el campo electromagnético en la lagrangiana.By assuming the expected functional form which describes composite fermions, the Hamiltonian is usually presented in a phenomenological way. In this paper, by using a U(1) × U(1) nonrelativistic gauge Lagrangian for electrons in an electromagnetic field, we show how to obtain the mean field Hamiltonian describing rigorously composite fermions in 2+1 dimensions. In addition, we compare these results with those obtained when considering the inclusion of a topological mass term for the electromagnetic field in the Lagrangian.Fil: Id Betan, Rodolfo Mohamed. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Manavella, Edmundo C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Repetto, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentin

Algebraic Gorkov solution in finite systems for the separable pairing interaction

An algebraic Quantum Field Theory formulation of separable pairing interaction for spherical finite systems is presented. The Lipkin formulation of the model Hamiltonian and model wave function is used. The Green function technique is applied to obtain the model energy through the spectral function. Closed equation for the many-body energy of the system is given and comparison with exact models are performed.Fil: Id Betan, Rodolfo Mohamed. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Repetto, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

Fluidics of Single and Double Blade Guillotine Vitrectomy Probes in Balanced Salt Solution and Artificial Vitreous

urpose: To assess the fluidics of double-vitreous cutter blade (DB) compared with single-blade (SB) guillotine with 23-, 25-, and 27-gauge vitrectomy probes. To assess flow characteristics and flow rates in viscous and viscoelastic fluids. Methods: We used Particle Image Velocimetry to measure the flow field close to the tip of each cutter probe and we derived kinematic quantities of interest, such as kinetic energy and acceleration. We performed measurements both on a balanced salt solution (BSS) and on a viscoelastic artificial vitreous (AV). Results: The flow rate is significantly higher with DB than SB vitrectomy probes, for a given pumping pressure and cutting rate. The fluid flow observed is very different between BSS and AV tests. Conclusions: The DB has more efficient fluidics than SB vitrectomy probe in all tested conditions. Fluid acceleration depends on the cutting frequency, especially in the case of measurements in AV. The flow rate strongly depends on the pressure and it is little affected by the cutting frequency, in a range of clinical interest. The 27-G DB produces flow rates similar to the 23- and 25-G SB, with significantly smaller acceleration. The flow induced in the AV is different from that in BSS and oscillates at different frequencies. Translational Relevance: DB cutters prove to be more efficient in terms of lower acceleration for a given flow rate. The latter is mainly controlled by aspiration pressure and less by cut rates. The influence of vitreous rheology deserves further investigations

A Mathematical Model of Interstitial Fluid Flow and Retinal Tissue Deformation in Macular Edema

Purpose: This study aims to develop a mathematical model to elucidate fluid circulation in the retina, focusing on the movement of interstitial fluid (comprising water and albumin) to understand the mechanisms underlying exudative macular edema (EME).Methods: The model integrates physiological factors such as retinal pigment epithelium (RPE) pumping, osmotic pressure gradients, and tissue deformation. It accounts for spatial variability in hydraulic conductivity (HC) across the retina and incorporates the structural role of Müller cells (MCs) in maintaining retinal stability.Results: The model predicts that tissue deformation is maximal at the center of the fovea despite fluid exudation from blood capillaries occurring elsewhere, aligning with clinical observations. Additionally, the model suggests that spatial variability in HC across the thickness of the retina plays a protective role against fluid accumulation in the fovea.Conclusions: Despite inherent simplifications and uncertainties in parameter values, this study represents a step toward understanding the pathophysiology of EME. The findings provide insights into the mechanisms underlying fluid dynamics in the retina and fluid accumulation in the foveal region, showing that the specific conformation of Müller cells is likely to play a key role

Mathematical model of blood and interstitial flow and lymph production in the liver.

We present a mathematical model of blood and interstitial flow in the liver. The liver is treated as a lattice of hexagonal \u2018classic\u2019 lobules, which are assumed to be long enough that end effects may be neglected and a two-dimensional problem considered. Since sinusoids and lymphatic vessels are numerous and small compared to the lobule, we use a homogenized approach, describing the sinusoidal and interstitial spaces as porous media. We model plasma filtration from sinusoids to the interstitium, lymph uptake by lymphatic ducts, and lymph outflow from the liver surface. Our results show that the effect of the liver surface only penetrates a depth of a few lobules\u2019 thickness into the tissue. Thus, we separately consider a single lobule lying sufficiently far from all external boundaries that we may regard it as being in an infinite lattice, and also a model of the region near the liver surface. The model predicts that slightly more lymph is produced by interstitial fluid flowing through the liver surface than that taken up by the lymphatic vessels in the liver and that the on-peritonealized region of the surface of the liver results in the total lymph production (uptake by lymphatics plus fluid crossing surface) being about 5 % more than if the entire surface were covered by the Glisson\u2013peritoneal membrane. Estimates of lymph outflow through the surface of the liver are in good agreement with experimental data. We also study the effect of non-physiological values of the controlling parameters, particularly focusing on the conditions of portal hypertension and ascites. To our knowledge, this is the first attempt to model lymph production in the liver. The model provides clinically relevant information about lymph outflow pathways and predicts the systemic response to pathological variations

Increasing efficiency of on-line shopping by optimizing the staff schedule

Problem proposed by: COOP Drive (online food shopping service provided by COOP Liguria), http://www.e-COOP.it/virtualShop/. The customers are making an online purchase and choose a time range for pick up. Making optimal staff scheduling such that each employee has ‘constant’ working hours, satisfying customers and employees in the same time. Constraints: Each employee can work at most 6 days a week. Each employee can work maximum 8 hours a day. Each employee needs to work continuous hours

Consenso chileno para la atención integral de niños y adultos con fibrosis quística

La Fibrosis Quística (FQ) es la enfermedad hereditaria de pronóstico reservado más frecuente en raza blanca. Desde el año 2003, Chile inicia un Programa Nacional de Fibrosis Quística, de carácter integral, dirigido por la Unidad de Salud Respiratoria del Ministerio de Salud. Hasta la fecha, los principales resultados del Programa registran una significativa mayor sobrevida (promedio 27 años) y una significativa reducción en la edad de diagnóstico de los pacientes ingresados desde 2006 en adelante. El acceso a la canasta GES (Garantías Explícitas en Salud), la implementación del tamizaje neonatal en algunas regiones del país, la organización y la constitución de equipos entrenados en FQ de diversas especialidades, ha contribuido a mejorar los resultados. Si bien las principales manifestaciones son del aparato respiratorio y digestivo, el carácter multisistémico de la FQ obliga a conocer los distintos aspectos involucrados en su manejo, a fin de optimizar los resultados del tratamiento y los recursos invertidos, tanto en el sector público como privado. Este documento es una revisión y actualización sobre los principales aspectos del diagnóstico, seguimiento y tratamiento de las manifestaciones respiratorias y no respiratorias de la FQ

Un modello analitico della fluodinamica del vitreo oculare liquefatto

Si presenta un modello teorico della fluodinamica del vitreo oculare liquefatto indotta dai movimenti saccadici dell'occhio. Il vitreo è schematizzato come un fluido Newtoniano incomprimibile in moto irrotazionale. Nel caso di vitreo liquefatto l'ipotesi di irrotazionalità del moto risulta giustificata poiché, durante i brevi e rapidi movimenti saccadici, si ha la formazione di uno strato limite viscoso alla parete, il cui spessore risulta trascurabile rispetto alle dimensioni del globo. La camera vitreale viene assimilata ad una sfera debolmente deformata in modo da mettere in conto la rientranza dovuta alla presenza del cristallino ed il fatto che l'asse antero-posteriore dell'occhio risulta, in condizioni fisiologiche, più corto rispetto a quello verticale ed a quello trasversale. Il problema per il potenziale della velocità assoluta viene risolto analiticamente in termini di armoniche sferiche. I risultati mostrano come la non sfericità del dominio generi nel vitreo un campo di moto caratterizzato da velocità significative e forte tridimensionalità. La distribuzione della velocità sul contorno suggerisce inoltre che l'irregolarità del dominio può modificare significativamente le tensioni tangenziali sulla retina rispetto al caso di moto all'interno di una sfera. Il modello consente la valutazione delle pressioni dinamiche sul contorno che possono avere un ruolo nella patogenesi del distacco di retina. Un'analisi semplificata, relativa al caso di moto piano bidimensionale e rotazione impulsiva dell'occhio, mostra come lo strato limite alla parete tenda a separare, in prossimità del cristallino, per valori dell'angolo di rotazione superiori a circa 17°