Floquet topological transitions in a driven one-dimensional topological insulator

The Su-Schrieffer-Heeger model of polyacetylene is a paradigmatic Hamiltonian exhibiting non-trivial edge states. By using Floquet theory we study how the spectrum of this one-dimensional topological insulator is affected by a time-dependent potential. In particular, we evidence the competition among different photon-assisted processes and the native topology of the unperturbed Hamiltonian to settle the resulting topology at different driving frequencies. While some regions of the quasienergy spectrum develop new gaps hosting Floquet edge states, the native gap can be dramatically reduced and the original edge states may be destroyed or replaced by new Floquet edge states. Our study is complemented by an analysis of Zak phase applied to the Floquet bands. Besides serving as a simple example for understanding the physics of driven topological phases, our results could find a promising test-ground in cold matter experiments

The Influence of Muslim Holidays on Stock Returns of the Kenyan Listed Firms’

This research aims to show the connection between Muslim holidays[1] and stock returns. The ‘event study methodology’ was employed and using a Kenyan sample of 20 listed firm-year data observations for the years 2013–2014 of the Nairobi Securities Exchange (NSE) 20-share index price movements, the authors analyze the effects of Muslim holidays[2] on stock returns. The results show that six out of the ten holidays studied had a positive effect on stock returns. The findings demonstrate that Muslim holidays affect stock returns of companies listed at the NSE. It can be inferred from the findings that the stock market is influenced by investor sentiments and dispositions. The study showed that, at some point, when investors ‘fail’ to be rational, this causes a stock market anomaly at the NSE. The study points out a conspicuous and important gap in knowledge and suggests recommendations for regulatory authorities in the light of the findings. Keywords: Efficient capital markets, investor rationality, Muslim holidays, market anomaly, stock market investment [1] These are religious practices whose aim, like all other fundamentals of Islam, is to imbibe piety and self-righteousness, and promote the spirit of sacrifice for a right cause. [2] In this study, the words holy day and holiday have been used interchangeably hence mean one and the same thing

A canine model of irreversible urethral sphincter insufficiency

OBJECTIVE To develop a canine model of external urinary sphincter insufficiency by creating irreversible damage to the sphincter, because there is a need for a reliable and reproducible large animal model for the study of stress urinary incontinence (SUI) caused by deficient sphincter function. MATERIALS AND METHODS About a quarter of the total external sphincter muscle was removed microsurgically from seven female dogs; three age-matched dogs served as normal controls. The dogs had standard urodynamic and radiographic studies before and at 1, 2, 3, 4 and 7 months after surgery. Three dogs were killed at 4 months and four at 7 months after surgery for tissue analyses. RESULTS The interventions produced a consistent outcome. Urodynamic studies showed a significant and sustained decrease in sphincter function, which included a static urethral pressure profile, stress urethral profile and detrusor leak-point pressure. Furthermore, in vivo pudendal nerve stimulation and organ-bath studies of the retrieved tissue strips confirmed the loss of sphincter tissue function. Histologically, absence of functional sphincter muscle was evident in the damaged sphincter region. CONCLUSIONS These results show that a reliable and reproducible canine model of irreversible sphincter insufficiency can be created by microsurgical removal of sphincter muscle tissue. This model of external sphincter insufficiency could be used for evaluating methods (e.g. cell therapies) for treating SUI

Creación de un centro de atención a la primera infancia para personal que estudia y labora en el Centro Regional Universitario de San Miguelito área Milla 8

El presente proyecto tiene como finalidad estudiar la creación de un Centro de Atención Integral a la Primera Infancia (CAIPI) en el futuro Centro Regional Universitario de San Miguelito en Milla 8 Transístmica dirigido a las madres estudiantes, docentes y administrativo que estudian la laboran para el cuidado de sus niños a edad temprana. La guardería o CAIPI brindaría respuesta a los niños estén en un lugar seguro, cómodo, atendido con un personal especializado garantizando manera óptima educación inicial, nutrición, asistencia médica, arte y folklore basado en una educación de ética y valores en beneficio de las madres del CRUSAM y la problemática que enfrenta. La investigación se basó en la observación de niños en horas de clase con sus madres, en la aplicación de las encuestas a las madres de la comunidad del CRUSAM, en el análisis del resultado que nos ayuda a determinar que el Proyecto de crear la construcción del CAIPI tiene una aceptación general; inquietud de nuestros estudiantes, docentes y administrativos que la Extensión Universitaria de San Miguelito con índice de población relevante debe ser apoyada para un rendimiento estudiantil, laboral, deserción de estudiantes, participación en actividades extracurriculares

Bilayered constructs aimed at osteochondral strategies : the influence of media supplements in the osteogenic and chondrogenic differentiation of amniotic fluid-derived stem cells

injuries and aging associated diseases that affect joints. This study reports the development of a bilayered scaffold, which consists of both bone and cartilage regions. On the other hand, amniotic fluid-derived stem cells (AFSCs) could be differentiated into either osteogenic or chondrogenic cells, respectively. In this study we have developed a bilayered scaffolding system, which includes a starch/polycaprolactone (SPCL) scaffold for osteogenesis and an agarose hydrogel for chondrogenesis. AFSC-seeded scaffolds were cultured for 1 or 2 weeks in an osteochondral-defined culture medium containing both osteogenic and chondrogenic differentiation factors. Additionally, the effect of the presence or absence of insulin-like growth factor-1 (IGF-1) in the culture medium was assessed. Cell viability and phenotypic expression were assessed within the constructs in order to determine the influence of the osteochondral differentiation medium. The results indicated that, after osteogenic differentiation, AFSCs that had been seeded onto SPCL scaffolds did not require osteochondral medium to maintain their phenotype, and they produced a protein-rich, mineralized extracellular matrix (ECM) for up to 2 weeks. However, AFSCs differentiated into chondrocyte-like cells appeared to require osteochondral medium, but not IGF-1, to synthesize ECM proteins and maintain the chondrogenic phenotype. Thus, although IGF-1 was not essential for creating osteochondral constructs with AFSCs in this study, the osteochondral supplements used appear to be important to generate cartilage in long-term tissue engineering approaches for osteochondral interfaces. In addition, constructs generated from agarose–SPCL bilayered scaffolds containing pre-differentiated AFSCs may be useful for potential applications in regeneration strategies for damaged or diseased joints.Fundação para a Ciência e a Tecnologia (FCT

Tenogenic potential of human stem cells from the amniotic fluid and adipose tissue

Tendons are highly prone to injury and the intrinsic hypocellularity and hypovascularity make their natural healing extremely slow and inefficient when severed damaged. Surgical repair with grafts is common but unsuccessful in a long term basis. The development of tissue engineering strategies based on stem cells explores a natural endogenous system of regeneration with potential for tendon application. We propose to establish biochemical culturing conditions to assess the tenogenic potential of human adipose stem cells (hASCs) and amniotic fluid-derived stem cells (hAFSCs), known for their proliferative and differentiation capacities. Since several growth factors (GFs) participate in tendon formation and ECM synthesis, these GFs were added to the culture medium to stimulate tenogenic differentiation of these cells. This study also envisions the application of hASCs and/or hAFSCs in cell-based strategies for tendon repair

Modelling study of the ability to diagnose acute rheumatic fever at different levels of the Ugandan healthcare system.

OBJECTIVE: To determine the ability to accurately diagnose acute rheumatic fever (ARF) given the resources available at three levels of the Ugandan healthcare system. METHODS: Using data obtained from a large epidemiological database on ARF conducted in three districts of Uganda, we selected variables that might positively or negatively predict rheumatic fever based on diagnostic capacity at three levels/tiers of the Ugandan healthcare system. Variables were put into three statistical models that were built sequentially. Multiple logistic regression was used to estimate ORs and 95% CI of predictors of ARF. Performance of the models was determined using Akaike information criterion, adjusted R2, concordance C statistic, Brier score and adequacy index. RESULTS: A model with clinical predictor variables available at a lower-level health centre (tier 1) predicted ARF with an optimism corrected area under the curve (AUC) (c-statistic) of 0.69. Adding tests available at the district level (tier 2, ECG, complete blood count and malaria testing) increased the AUC to 0.76. A model that additionally included diagnostic tests available at the national referral hospital (tier 3, echocardiography, anti-streptolysin O titres, erythrocyte sedimentation rate/C-reactive protein) had the best performance with an AUC of 0.91. CONCLUSIONS: Reducing the burden of rheumatic heart disease in low and middle-income countries requires overcoming challenges of ARF diagnosis. Ensuring that possible cases can be evaluated using electrocardiography and relatively simple blood tests will improve diagnostic accuracy somewhat, but access to echocardiography and tests to confirm recent streptococcal infection will have the greatest impact

Observation of Bose-Einstein Condensation in a Strong Synthetic Magnetic Field

Extensions of Berry's phase and the quantum Hall effect have led to the discovery of new states of matter with topological properties. Traditionally, this has been achieved using gauge fields created by magnetic fields or spin orbit interactions which couple only to charged particles. For neutral ultracold atoms, synthetic magnetic fields have been created which are strong enough to realize the Harper-Hofstadter model. Despite many proposals and major experimental efforts, so far it has not been possible to prepare the ground state of this system. Here we report the observation of Bose-Einstein condensation for the Harper-Hofstadter Hamiltonian with one-half flux quantum per lattice unit cell. The diffraction pattern of the superfluid state directly shows the momentum distribution on the wavefuction, which is gauge-dependent. It reveals both the reduced symmetry of the vector potential and the twofold degeneracy of the ground state. We explore an adiabatic many-body state preparation protocol via the Mott insulating phase and observe the superfluid ground state in a three-dimensional lattice with strong interactions.Comment: 6 pages, 5 figures. Supplement: 6 pages, 4 figure

Abelian gauge potentials on cubic lattices

The study of the properties of quantum particles in a periodic potential subject to a magnetic field is an active area of research both in physics and mathematics; it has been and it is still deeply investigated. In this review we discuss how to implement and describe tunable Abelian magnetic fields in a system of ultracold atoms in optical lattices. After discussing two of the main experimental schemes for the physical realization of synthetic gauge potentials in ultracold set-ups, we study cubic lattice tight-binding models with commensurate flux. We finally examine applications of gauge potentials in one-dimensional rings.Comment: To appear on: "Advances in Quantum Mechanics: Contemporary Trends and Open Problems", G. Dell'Antonio and A. Michelangeli eds., Springer-INdAM series 201