Improved numerical methods for infinite spin chains with long-range interactions

We present several improvements of the infinite matrix product state (iMPS) algorithm for finding ground states of one-dimensional quantum systems with long-range interactions. As a main new ingredient we introduce the superposed multi-optimization (SMO) method, which allows an efficient optimization of exponentially many MPS of different length at different sites all in one step. Hereby the algorithm becomes protected against position dependent effects as caused by spontaneously broken translational invariance. So far, these have been a major obstacle to convergence for the iMPS algorithm if no prior knowledge of the systems translational symmetry was accessible. Further, we investigate some more general methods to speed up calculations and improve convergence, which might be partially interesting in a much broader context, too. As a more special problem, we also look into translational invariant states close to an invariance braking phase transition and show how to avoid convergence into wrong local minima for such systems. Finally, we apply the new methods to polar bosons with long-range interactions. We calculate several detailed Devil's Staircases with the corresponding phase diagrams and investigate some supersolid properties.Comment: Main text: 17 pages plus references, 8 figures. Supplementary info: 6 pages. v2: improved presentation and more results adde

Nonequilibrium electron transport using the density matrix renormalization group

We extended the Density Matrix Renormalization Group method to study the real time dynamics of interacting one dimensional spinless Fermi systems by applying the full time evolution operator to an initial state. As an example we describe the propagation of a density excitation in an interacting clean system and the transport through an interacting nano structure

Understanding tribological behavior of complex gel systems for personal care applications using surrogate skin and their bulk rheology

Creams and lotions based on oil-in-water emulsions with polymers are commonly used to treat dry skin conditions. Since the accumulation of traditional surfactants on the skin can promote irritation, an alternative is the use of hydrogenated phosphatidylcholine (HPC), a type of phospholipid that can form a lipid lamellar structure similar to the stratum corneum, the outermost layer of the epidermis which acts as a skin barrier. This research aims to investigate the effect of composition on the rheological and tribological characteristics in systems with HPC as surfactant and to find relationships between rheological and tribological properties to help predicting sensory perception of emulsions for skincare applications. For tribology experiments we used a ball-on-disk configuration to obtain friction curves using different disk materials to mimic the skin surface (PDMS and artificial skin, Bioskin™), while for bulk rheology studies we used dynamic and steady shear experiments. We examine how the addition of different amounts of HPC and polymers with different hydrophobicity affects friction and lubrication regimes from the tribological standpoint and the viscoelasticity, yield stress, and gel formation from the rheological standpoint. The bulk rheology shows that the studied systems are shear thinning and have gel-like behavior. The effect of each component was investigated by going from a simple system (polymer and water) to the more complex system. Systems containing a hydrophobically modified polyacrylic acid lightly crosslinked showed lower yield stresses and lower moduli than systems with carbomer type polymer. Analogous experiments were carried out in tribology. In the range of entrainment speed investigated, the friction coefficients in the boundary regime were lower for diluted systems containing the hydrophobically modified polymer than for systems containing the carbomer type polymer. The Stribeck curves obtained for each of the systems are compared for different polymer types and related to the bulk rheology results to obtain physical insights into these complex systems

Conservative surgical treatment in cervical dysplastic lesions associated with cystorectocele

The treatment of cervical intraepithelial neoplasia aims at removing the squamocolumnar junction area, including abnormal tissues, up to the healthy tissue. Old postpartum perineal tears associated with cystorectocele, hypertrophic cervical elongation, and first and second degree uterine prolapse are pelvic static disorders. Particular aspects of pelvic-genital static disorder are related to the vulnerability of the pelvic-perineal floor during birth. On the occasion of birth, especially when there are different forms of dystocia during labor, the degradation of soft pelvic, genital, and vaginal-perineal tissues can occur. The objective of this study was to re-evaluate the conservative treatment of cervical dysplasia, depending on the degree of cervical lesions, the surface extension, the age of the patients, and the pathology associated with cervical lesions – colpocele, cystorectocele, and urinary incontinence in the old postpartum perineal tears. In order to solve the three types of concomitant lesions, we used the Manchester operation: the anterior colporrhaphy with the recalibration of the urethra and the suspension of the cystocele, the minimal colpectomy, the lesional cervical amputation with the anterior fixation of the parameters, and the posterior colpoperineorrhaphy with high myorrhaphy of the levator ani muscles. The decision on the management of cervical dysplasia has taken into account the degree of cervical lesions, the extension on the surface, the patients’ age and the pregnancy planning, and the pathology associated with cervical lesions. The Manchester operation is a conservative surgical procedure, effective in women under 45 years old, multiparous, with present genital activity, with dysplastic cervical lesions and cystorectocele. It also solves cystorectocele, cervical dysplasia, hypertrophic cervical elongation, and first and second degree uterine prolapse

Casimir interactions of an object inside a spherical metal shell

We investigate the electromagnetic Casimir interactions of an object contained within an otherwise empty, perfectly conducting spherical shell. For a small object we present analytical calculations of the force, which is directed away from the center of the cavity, and the torque, which tends to align the object opposite to the preferred alignment outside the cavity. For a perfectly conducting sphere as the interior object, we compute the corrections to the proximity force approximation (PFA) numerically. In both cases the results for the interior configuration match smoothly onto those for the corresponding exterior configuration.Comment: 4 pages, 3 figure

5-HT2a receptor in mPFC influences context-guided reconsolidation of object memory in perirhinal cortex

Context-dependent memories may guide adaptive behavior relaying in previous experience while updating stored information through reconsolidation. Retrieval can be triggered by partial and shared cues. When the cue is presented, the most relevant memory should be updated. In a contextual version of the object recognition task, we examined the effect of medial PFC (mPFC) serotonin 2a receptor (5-HT2aR) blockade during retrieval in reconsolidation of competing objects memories. We found that mPFC 5-HT2aR controls retrieval and reconsolidation of object memories in the perirhinal cortex (PRH), but not in the dorsal hippocampus in rats. Also, reconsolidation of objects memories in PRH required a functional interaction between the ventral hippocampus and the mPFC. Our results indicate that in the presence of conflicting information at retrieval, mPFC 5-HT2aR may facilitate top-down context-guided control over PRH to control the behavioral response and object memory reconsolidation.Fil: Morici, Juan Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiología y Biofísica Bernardo Houssay; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Miranda, Magdalena. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Gallo, Francisco Tomás. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Zanoni Saad, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; Argentina. Universidad Favaloro; ArgentinaFil: Bekinschtein, Pedro Alejandro. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Weisstaub, Noelia V.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiología y Biofísica Bernardo Houssay; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; Argentin