Rotation periods of exoplanet host stars

The stellar rotation periods of 10 exoplanet host stars have been determined using newly analysed CaII H&K flux records from the Mount Wilson Observatory and Strömgren b, y photometric measurements from Tennessee State University's automatic photometric telescopes at the Fairborn Observatory. Five of the rotation periods have not previously been reported, with that of HD 130322 very strongly detected at Prot = 26.1 +/- 3.5 d. The rotation periods of five other stars have been updated using new data. We use the rotation periods to derive the line-of-sight inclinations of the stellar rotation axes, which may be used to probe theories of planet formation and evolution when combined with the planetary orbital inclination found from other methods. Finally, we estimate the masses of 14 exoplanets under the assumption that the stellar rotation axis is aligned with the orbital axis. We calculate the mass of HD 92788 b (28 MJ) to be within the low-mass brown dwarf regime and suggest that this object warrants further investigation to confirm its true nature.

Burkholderia cenocepacia requires a periplasmic HtrA protease for growth under thermal and osmotic stress and for survival in vivo

Burkholderia cenocepacia, a member of the B. cepacia complex, is an opportunistic pathogen that causes serious infections in patients with cystic fibrosis. We identified a six-gene cluster in chromosome 1 encoding a two-component regulatory system (BCAL2831 and BCAL2830) and an HtrA protease (BCAL2829) hypothesized to play a role in the B. cenocepacia stress response. Reverse transcriptase PCR analysis of these six genes confirmed they are cotranscribed and comprise an operon. Genes in this operon, including htrA, were insertionally inactivated by recombination with a newly created suicide plasmid, pGPOmegaTp. Genetic analyses and complementation studies revealed that HtrA(BCAL2829) was required for growth of B. cenocepacia upon exposure to osmotic stress (NaCl or KCl) and thermal stress (44 degrees C). In addition, replacement of the serine residue in the active site with alanine (S245A) and deletion of the HtrA(BCAL2829) PDZ domains demonstrated that these areas are required for protein function. HtrA(BCAL2829) also localizes to the periplasmic compartment, as shown by Western blot analysis and a colicin V reporter assay. Using the rat agar bead model of chronic lung infection, we also demonstrated that inactivation of the htrA gene is associated with a bacterial survival defect in vivo. Together, our data demonstrate that HtrA(BCAL2829) is a virulence factor in B. cenocepacia.

Cardiovascular actions of trout urotensin II in the conscious trout, Oncorhynchus mykiss

The central and peripheral cardiovascular effects of synthetic trout urotensin II (UII) were investigated in the conscious rainbow trout. Intracerebroventricular injection of 50 pmol UII produced a slight (3%) but significant (P < 0.05) increase in heart rate but had no effect on mean arterial blood pressure. Injection of 500 pmol UII icy produced a significant (P < 0.05) rise (8%) in blood pressure with no change in heart rate. In contrast to the weak presser effect of centrally administered UII, intra-arterial injection of UII produced a dose-dependent increase in arterial blood pressure and decrease in heart rate with significant (P < 0.05) effects on both parameters observed at a dose of 25 pmol. Higher doses of the peptide produced a sustained decrease in cardiac output that accompanied the bradycardia and rise in arterial blood pressure. The UII-induced bradycardia, but not the increase in pressure, was abolished by pretreatment with phentolamine. Trout UII produced a sustained and dose-dependent contraction of isolated vascular rings prepared from trout efferent branchial [-log 50% of the concentration producing maximal contraction (pD(2)) = 8.30] and celiacomesenteric (pD(2) = 8.22) arteries but was without effects on vascular rings from the anterior cardinal vein. The data indicate that the presser effect of UII in trout is mediated predominantly, if not exclusively, by an increase in systemic vascular resistance. The UII-induced hypertensive response does not seem to involve release of catecholamines, but the bradycardia may arise from adrenergic-mediated activation of cardioinhibitory baroreflexes.

The Computational Complexity of Dominance and Consistency in CP-Nets

We investigate the computational complexity of testing dominance and consistency in CP-nets. Previously, the complexity of dominance has been determined for restricted classes in which the dependency graph of the CP-net is acyclic. However, there are preferences of interest that define cyclic dependency graphs; these are modeled with general CP-nets. In our main results, we show here that both dominance and consistency for general CP-nets are PSPACE-complete. We then consider the concept of strong dominance, dominance equivalence and dominance incomparability, and several notions of optimality, and identify the complexity of the corresponding decision problems. The reductions used in the proofs are from STRIPS planning, and thus reinforce the earlier established connections between both areas.

Developing Approaches for Solving a Telecommunications Feature Subscription Problem

Call control features (e.g., call-divert, voice-mail) are primitive options to which users can subscribe off-line to personalise their service. The configuration of a feature subscription involves choosing and sequencing features from a catalogue and is subject to constraints that prevent undesirable feature interactions at run-time. When the subscription requested by a user is inconsistent, one problem is to find an optimal relaxation, which is a generalisation of the feedback vertex set problem on directed graphs, and thus it is an NP-hard task. We present several constraint programming formulations of the problem. We also present formulations using partial weighted maximum Boolean satisfiability and mixed integer linear programming. We study all these formulations by experimentally comparing them on a variety of randomly generated instances of the feature subscription problem.

On the Qualitative Comparison of Decisions Having Positive and Negative Features

Making a decision is often a matter of listing and comparing positive and negative arguments. In such cases, the evaluation scale for decisions should be considered bipolar, that is, negative and positive values should be explicitly distinguished. That is what is done, for example, in Cumulative Prospect Theory. However, contrary to the latter framework that presupposes genuine numerical assessments, human agents often decide on the basis of an ordinal ranking of the pros and the cons, and by focusing on the most salient arguments. In other terms, the decision process is qualitative as well as bipolar. In this article, based on a bipolar extension of possibility theory, we define and axiomatically characterize several decision rules tailored for the joint handling of positive and negative arguments in an ordinal setting. The simplest rules can be viewed as extensions of the maximin and maximax criteria to the bipolar case, and consequently suffer from poor decisive power. More decisive rules that refine the former are also proposed. These refinements agree both with principles of efficiency and with the spirit of order-of-magnitude reasoning, that prevails in qualitative decision theory. The most refined decision rule uses leximin rankings of the pros and the cons, and the ideas of counting arguments of equal strength and cancelling pros by cons. It is shown to come down to a special case of Cumulative Prospect Theory, and to subsume the “Take the Best” heuristic studied by cognitive psychologists.

Investigating autonomic control of the cardiovascular system: a battery of simple tests

Sympathetic and parasympathetic divisions of the autonomic nervous system constantly control the heart (sympathetic and parasympathetic divisions) and blood vessels (predominantly the sympathetic division) to maintain appropriate blood pressure and organ blood flow over sometimes widely varying conditions. This can be adversely affected by pathological conditions that can damage one or both branches of autonomic control. The set of teaching laboratory activities outlined here uses various interventions, namely, 1) the heart rate response to deep breathing, 2) the heart rate response to a Valsalva maneuver, 3) the heart rate response to standing, and 4) the blood pressure response to standing, that cause fairly predictable disturbances in cardiovascular parameters in normal circumstances, which serve to demonstrate the dynamic control of the cardiovascular system by autonomic nerves. These tests are also used clinically to help investigate potential damage to this control.

Apoptosis induction by oxidized glycated LDL in human retinal capillary pericytes is independent of activation of MAPK signaling pathways

Pericyte loss is a cardinal feature of early diabetic retinopathy. We previously reported that highly oxidized-glycated low density lipoprotein (HOG-LDL) induces pericyte apoptosis in vitro. In this study, we investigated the role of the mitogen-activated protein kinase (MAPK) signaling pathways in HOG-LDL-induced apoptosis in human pericytes.

Probabilistic Inference in Credal Networks: New Complexity Results

Credal networks are graph-based statistical models whose parameters take values in a set, instead of being sharply specified as in traditional statistical models (e.g., Bayesian networks). The computational complexity of inferences on such models depends on the irrelevance/independence concept adopted. In this paper, we study inferential complexity under the concepts of epistemic irrelevance and strong independence. We show that inferences under strong independence are NP-hard even in trees with binary variables except for a single ternary one. We prove that under epistemic irrelevance the polynomial-time complexity of inferences in credal trees is not likely to extend to more general models (e.g., singly connected topologies). These results clearly distinguish networks that admit efficient inferences and those where inferences are most likely hard, and settle several open questions regarding their computational complexity. We show that these results remain valid even if we disallow the use of zero probabilities. We also show that the computation of bounds on the probability of the future state in a hidden Markov model is the same whether we assume epistemic irrelevance or strong independence, and we prove an analogous result for inference in Naive Bayes structures. These inferential equivalences are important for practitioners, as hidden Markov models and Naive Bayes networks are used in real applications of imprecise probability.

Solving Limited Memory Influence Diagrams

We present a new algorithm for exactly solving decision making problems represented as influence diagrams. We do not require the usual assumptions of no forgetting and regularity; this allows us to solve problems with simultaneous decisions and limited information. The algorithm is empirically shown to outperform a state-of-the-art algorithm on randomly generated problems of up to 150 variables and 10^64 solutions. We show that these problems are NP-hard even if the underlying graph structure of the problem has low treewidth and the variables take on a bounded number of states, and that they admit no provably good approximation if variables can take on an arbitrary number of states.

MHD wave modes resolved in fine-scale chromospheric magnetic structures

Within the last decade, due to significant improvements in the spatial and temporal resolution of chromospheric data, magneto hydrodynamic (MHD)wave studies in this fascinating region of the Sun's atmosphere have risen to the forefront of solar physics research. In this review we begin by reviewing the challenges and debates that have manifested in relation to MHD wave mode identification in fine-scale chromosphericmagnetic structures, including spicules, fibrils and mottles. Next we goon to discuss how the process of accurately identifying MHD wave modes also has a crucial role to play in estimating their wave energy flux.This is of cardinal importance for estimating what the possible contribution of MHD waves is to solar atmospheric heating. Finally, we detail how such advances in chromospheric MHD wave studies have also allowed us, for the first time, to implement cutting-edge magneto seismological techniques that provide new insight into the sub-resolution plasma structuring of the lower solar atmosphere.

Modulation of human corticospinal excitability by paired associative stimulation

Paired Associative Stimulation (PAS) has come to prominence as a potential therapeutic intervention for the treatment of brain injury/disease, and as an experimental method with which to investigate Hebbian principles of neural plasticity in humans. Prototypically, a single electrical stimulus is directed to a peripheral nerve in advance of transcranial magnetic stimulation (TMS) delivered to the contralateral primary motor cortex (M1). Repeated pairing of the stimuli (i.e., association) over an extended period may increase or decrease the excitability of corticospinal projections from M1, in manner that depends on the interstimulus interval (ISI). It has been suggested that these effects represent a form of associative long-term potentiation (LTP) and depression (LTD) that bears resemblance to spike-timing dependent plasticity (STDP) as it has been elaborated in animal models. With a large body of empirical evidence having emerged since the cardinal features of PAS were first described, and in light of the variations from the original protocols that have been implemented, it is opportune to consider whether the phenomenology of PAS remains consistent with the characteristic features that were initially disclosed. This assessment necessarily has bearing upon interpretation of the effects of PAS in relation to the specific cellular pathways that are putatively engaged, including those that adhere to the rules of STDP. The balance of evidence suggests that the mechanisms that contribute to the LTP- and LTD-type responses to PAS differ depending on the precise nature of the induction protocol that is used. In addition to emphasizing the requirement for additional explanatory models, in the present analysis we highlight the key features of the PAS phenomenology that require interpretation.