A random walker on a ratchet potential: Effect of a non Gaussian noise

We analyze the effect of a colored non Gaussian noise on a model of a random walker moving along a ratchet potential. Such a model was motivated by the transport properties of motor proteins, like kinesin and myosin. Previous studies have been realized assuming white noises. However, for real situations, in general we could expect that those noises be correlated and non Gaussian. Among other aspects, in addition to a maximum in the current as the noise intensity is varied, we have also found another optimal value of the current when departing from Gaussian behavior. We show the relevant effects that arise when departing from Gaussian behavior, particularly related to current's enhancement, and discuss its relevance for both biological and technological situations.Comment: Submitted to Europ.Phys. J. B (LaTex, 16 pgs, 8 figures

Transition from anomalous to normal hysteresis in a system of coupled Brownian motors: a mean field approach

We address a recently introduced model describing a system of periodically coupled nonlinear phase oscillators submitted to multiplicative white noises, wherein a ratchet-like transport mechanism arises through a symmetry-breaking noise-induced nonequilibrium phase transition. Numerical simulations of this system reveal amazing novel features such as negative zero-bias conductance and anomalous hysteresis, explained resorting to a strong-coupling analysis in the thermodynamic limit. Using an explicit mean-field approximation we explore the whole ordered phase finding a transition from anomalous to normal hysteresis inside this phase, estimating its locus and identifying (within this scheme) a mechanism whereby it takes place.Comment: RevTex, 21 pgs, 15 figures. Submited to Physical Review E (2000

Limit cycle induced by multiplicative noise in a system of coupled Brownian motors

We study a model consisting of $N$ nonlinear oscillators with {\em global periodic} coupling and {\em local multiplicative} and additive noises. The model was shown to undergo a nonequilibrium phase transition towards a broken-symmetry phase exhibiting noise-induced "ratchet" behavior. A previous study \cite{[7]} focused on the relationship between the character of thehysteresis loop, the number of ``homogeneous'' mean-field solutions and the shape of the stationary mean-field probability distribution function. Here we show --as suggested by the absence of stable solutions when the load force is beyond a critical value-- the existence of a limit cycle induced by both:multiplicative noise and {\em global periodic} coupling.Comment: Submitted to Phys. Rev. E, RevTex, 18 pgs, 5 figure

Resonant phenomena in extended chaotic systems subject to external noise: the Lorenz'96 model case

We investigate the effects of a time-correlated noise on an extended chaotic system. The chosen model is the Lorenz'96, a kind of "toy" model used for climate studies. Through the analysis of the system's time evolution and its time and space correlations, we have obtained numerical evidence for two stochastic resonance-like behavior. Such behavior is seen when both, the usual and a generalized signal-to-noise ratio function are depicted as a function of the external noise intensity or the system size. The underlying mechanism seems to be associated to a "noise-induced chaos reduction". The possible relevance of these and other findings for an "optimal" climate prediction are discussed.Comment: Submitted to Europhysics Letters (LaTex, 12 pgs, 5 figures

Stochastic resonance between dissipative structures in a bistable noise-sustained dynamics

We study an extended system that without noise shows a monostable dynamics, but when submitted to an adequate multiplicative noise, an effective bistable dynamics arise. The stochastic resonance between the attractors of the \textit{noise-sustained dynamics} is investigated theoretically in terms of a two-state approximation. The knowledge of the exact nonequilibrium potential allows us to obtain the output signal-to-noise ratio. Its maximum is predicted in the symmetric case for which both attractors have the same nonequilibrium potential value.Comment: RevTex, 13 pages, 6 figures, accepted in Physical Review

Phase Transitions and Adsorption Isotherm in Multilayer Adsorbates with Lateral Interactions

We analyze here a model for an adsorbate system composed of many layers by extending a theoretical approach used to describe pattern formation on a monolayer of adsorbates with lateral interactions. The approach shows, in addition to a first order phase transition in the first layer, a transition in the second layer together with evidence of a "cascade" of transitions if more layers are included. The transition profiles, showing a staircase structure, corroborate this picture. The adsorption isotherm that came out of this approach is in qualitative agreement with numerical and experimental results.Comment: Submited to Physica A, LaTex, 22 pgs, 6 figure

Barriers to institutional investment in rental housing: a systematic review of market risks.

Housing practitioners and policy experts are advocating for an expansion in rental housing supply in contemporary cities around the world. The objective is to convince institutional investors to include rental housing investment in their investment portfolio to contribute to boosting housing supply. Unfortunately, the rental sector is characterized by numerous uncertainties and challenges, making it unattractive to institutional investors. With the growing attention to institutional investors in various housing market contexts, an understanding of the market risks (also known as barriers), is useful to inform future research and policymaking. Using a systematic literature review methodology, this paper synthesizes the extant literature on the market risks inhibiting institutional investment in rental housing. The review finds the following barriers: low profitability, non-progressive rent control policies, unclear target group for rented projects, poor landlord-tenant relations, inadequate property management and unreliable property market information. Among all the barriers identified, low profitability and inadequate property management had great influence on their investment decision. Firstly, institutional investors perceive rental housing investment as less profitable and unattractive in terms of project performance. Secondly, the lack of supporting structures for the property management sector contributes to derailing rental yields. Furthermore, the review finds that the position of policymakers on target grouping was unclear for projects under government assistance. In view of the identified barriers, this paper concludes that, although the idea of expanding rental housing supply seems laudable, ignoring these problems may be detrimental to housing markets in the long run. Rental markets in many countries are volatile, and not ready to receive institutional investors fully into the sector. An expanded rental sector could be improved or advanced if policy makers take the appropriate steps to resolve the identified challenges and make adequate structural preparations for large scale rental housing supply

Use of anakinra in severe COVID-19: a case report

Coronavirus Disease 19 is a global healthcare emergency with high lethality rate. Relevant inflammatory cytokine storm is associated with severity of disease and IL1 inhibition is a cornerstone treatment for hyperinflammatory diseases. We present here the case of a patient with critical COVID-19 successfully treated with IL-1 receptor antagonist (anakinra)

The emergence of REITs in Ghana

Real estate investment trusts (REITs) are evolving in Ghana’s real estate market. As at mid-2021, Republic Bank and GCB Securities were the two publicly known institutions operating REITs in the country. With the passage of the 2019 REIT guidelines, all existing REITs were rendered invalid, pursuant to provisions that, REITs must be approved by the Securities and Exchange Commission of Ghana. Using exploratory qualitative methods, the study investigates on-going developments surrounding the formulation of REITs in Ghana. Interviews were conducted with institutional investors and policy experts on their perception on the new REIT guidelines and the conditionalities needed for developing a REIT sector in Ghana. Institutional investors were largely receptive of the new REIT guidelines but at the same time not enthusiastic about venturing into it. They exclaimed that, unless REIT yields are proven to be competitive against their existing assets, they may not consider it in the short term. To develop Ghana’s first REIT sector, there are three conditions to be met, namely, creating a conducive macroeconomic environment, improving the state of the real estate industry, and developing an effective legal and regulatory framework. The study concludes that, there is a market for REITs in Ghana to serve institutional investors such as pension funds, insurance companies, private equity funds etc. However, the right structures must be created to usher in more advanced forms of indirect real estate investments. Additionally, real estate companies must be encouraged to trade publicly on the Ghana Stock Exchange once the opportunity presents itself, to expand their financing options. The implementation of the REIT guideline is a major milestone towards negotiating, establishing, and operating REITs in Ghana

Flow cytometric analysis of DNA content in human ovarian cancers.

A total of 155 samples from 101 patients with ovarian cancer were investigated using flow cytometry to evaluate the DNA index and the percentage of cells in the various cell cycle phases. Thirty-four samples were DNA diploid tumours, while the other 121 were DNA aneuploid tumours. The DNA index was very stable in different sites and over time in the same patient. Tumour stage and ploidy were significantly associated: stages III and IV tumour stage were more likely to be DNA aneuploid. Patients with residual tumour size at first surgery greater than 2 cm had a significantly larger number of DNA aneuploid than DNA diploid tumours. The DNA index was also related to the degree of differentiation of the tumours. The percentage of cells in the S phase of the cell cycle was significantly higher in DNA aneuploid and in poorly differentiated tumours than DNA diploid and well differentiated tumours. Multivariate analysis using the Cox model showed that the DNA index and the percentage of cells in S phase were not independent prognostic variables in this study. Prospectively collected data should be accumulated before assigning the DNA index an important role as a biological prognostic factor in ovarian cancer