Adaptation to criticality through organizational invariance in embodied agents

Many biological and cognitive systems do not operate deep within one or other regime of activity. Instead, they are poised at critical points located at phase transitions in their parameter space. The pervasiveness of criticality suggests that there may be general principles inducing this behaviour, yet there is no well-founded theory for understanding how criticality is generated at a wide span of levels and contexts. In order to explore how criticality might emerge from general adaptive mechanisms, we propose a simple learning rule that maintains an internal organizational structure from a specific family of systems at criticality. We implement the mechanism in artificial embodied agents controlled by a neural network maintaining a correlation structure randomly sampled from an Ising model at critical temperature. Agents are evaluated in two classical reinforcement learning scenarios: the Mountain Car and the Acrobot double pendulum. In both cases the neural controller appears to reach a point of criticality, which coincides with a transition point between two regimes of the agent's behaviour. These results suggest that adaptation to criticality could be used as a general adaptive mechanism in some circumstances, providing an alternative explanation for the pervasive presence of criticality in biological and cognitive systems.Comment: arXiv admin note: substantial text overlap with arXiv:1704.0525

On the Mailbox Problem

The Mailbox Problem was described and solved by Aguilera, Gafni, and Lamport in their 2010 DC paper with an algorithm that uses two flag registers that carry 14 values each. An interesting problem that they ask is whether there is a mailbox algorithm with smaller flag values. We give a positive answer by describing a mailbox algorithm with 6 and 4 values in the two flag registers

Frame synchronization performance and analysis

The analysis used to generate the theoretical models showing the performance of the frame synchronizer is described for various frame lengths and marker lengths at various signal to noise ratios and bit error tolerances

Nonlocality effects on Color Spin Locking condensates

We consider the color spin locking (CSL) phase of two-flavor quark matter at zero temperature for nonlocal instantaneous, separable interactions. We employ a Lorentzian-type form factor allowing a parametric interpolation between the sharp (Nambu-Jona-Lasinio (NJL) model) and very smooth (e.g. Gaussian) cut-off models for systematic studies of the influence on the CSL condensate the deviation from the NJL model entails. This smoothing of the NJL model form factor shows advantageous features for the phenomenology of compact stars: (i) a lowering of the critical chemical potential for the onset of the chiral phase transition as a prerequisite for stability of hybrid stars with extended quark matter cores and (ii) a reduction of the smallest pairing gap to the order of 100 keV, being in the range of values interesting for phenomenological studies of hybrid star cooling evolution.Comment: 8 pages, 8 figures, 1 table, accepted for publication in Phys.Rev.

Twenty years of ‘Law and Finance’: time to take law seriously

This ‘state of the art’ essay provides a comprehensive discussion of the Law and Finance School (LFS) literature. We show that the first two decades of the LFS have focused on empirically investigating the question ‘does law matter?’ Yet, despite the centrality of law to the LFS, it is based on an incoherent theory of law, which leads to shortcomings in the conceptualization and empirical testing of its hypotheses. We also observe that, rather than addressing this deficiency, the LFS has moved its focus to the contentious concept of ‘legal origin’. We argue that the LFS needs to take law more seriously by returning to its initial focus on the substance of legal rules and by addressing the theoretical question ‘how does law matter?’ We propose venues for future research to develop a solid theoretical framework that would put the empirical investigation of law’s impact on economic outcomes on a more solid footing

Geminivirus Rep Protein Interferes with the Plant DNA Methylation Machinery and Suppresses Transcriptional Gene Silencing

Viruses are masters at circumventing host defenses and manipulating the cellular environment for their own benefit. The replication of the largest known family of single-stranded DNA viruses, Geminiviridae, is impaired by DNA methylation but the fact that plants might use methylation as a defense against geminiviruses and the impact that viral genome methylation may have during the infection, remain controversial. We have found that geminiviruses reduce the expression of the plant maintenance DNA methyltransferases, MET1 and CMT3, in both, locally and systemically infected tissues. Furthermore, we demonstrated that the virus-mediated repression of these two maintenance DNA methyltransferases is widely spread among different geminivirus species and we have identified Rep as the geminiviral protein responsible for the repression of MET1 and CMT3. The presence of Rep, suppresses transcriptional gene silencing (TGS) of an Arabidopsis transgene and of host loci whose expression is strongly controlled by MET1. Bisulfite sequencing analyses showed that the expression of Rep caused a substantial reduction in the levels of DNA methylation at certain loci at CG sites. The biological relevance of these findings and the role of Rep as a TGS suppressor will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Dasatinib in chronic myeloid leukemia: a review

Deregulated BCR-ABL tyrosine kinase (TK) activity is the molecular marker for chronic myeloid leukemia (CML), which provides an identifiable target for developing therapeutic agents. Imatinib mesylate, a BCR-ABL TK inhibitor, is the frontline therapy for CML. Despite the stunning efficacy of this agent, a small number of patients develop a suboptimal response or resistance to imatinib. In newly diagnosed patients with chronic phase CML, the rate of resistance to imatinib at 4 years was up to 20%, increasing to 70% to 90% for patients in the accelerated/blastic phase. Resistance to imatinib led to the development of novel TK inhibitors such as dasatinib. Several clinical trials have reported more durable complete hematologic and cytogenetic responses with this agent in patients who are resistant or intolerant to imatinib. Dasatinib is well tolerated and has broad efficacy, resulting in durable responses in patients with any BCR-ABL mutation except for T3151 and mutations in codon 317 – most commonly F317L – including mutations that were highly resistant to imatinib, such as L248, Y253, E255, F359, and H396. Dasatinib is recommended for CML in chronic, blastic or accelerated phase that is resistant or intolerant to imatinib. Dasatinib was approved by the FDA at 100 mg once daily as the starting dose in patients with chronic phase CML and at 70 mg twice daily in patients with accelerated or blastic phase CML. Various clinical trial results provided evidence that resistance to one TK inhibitor can be reversed with the use of a different TK inhibitor (TKI). Other second-generation TKIs with activity in CML include nilotinib, bosutinib and INNO 406. New molecules, such as the inhibitor of Aurora family serine-threonine kinases, MK0457, which has antileukemic activity in CML associated with a T315I mutation, are being investigated. Allogeneic hematopoietic stem cell transplantation remains an option for selected patients

Asymptotic iteration method for eigenvalue problems

An asymptotic interation method for solving second-order homogeneous linear differential equations of the form y'' = lambda(x) y' + s(x) y is introduced, where lambda(x) \neq 0 and s(x) are C-infinity functions. Applications to Schroedinger type problems, including some with highly singular potentials, are presented.Comment: 14 page