Time-Distance Imaging of Solar Far-Side Active Regions

It is of great importance to monitor large solar active regions in the far-side of the Sun for space weather forecast, in particular, to predict their appearance before they rotate into our view from the solar east limb. Local helioseismology techniques, including helioseismic holography and time-distance, have successfully imaged solar far-side active regions. In this Letter, we further explore the possibility of imaging and improving the image quality of solar far-side active regions by use of time-distance helioseismology. In addition to the previously used scheme with four acoustic signal skips, a five-skip scheme is also included in this newly developed technique. The combination of both four- and five-skip far-side images significantly enhances the signal-to-noise ratio in the far-side images, and reduces spurious signals. The accuracy of the far-side active region imaging is also assessed using one whole year solar observation.Comment: 13 pages, 5 figures, accepted by ApJ Letter

Signaling and Tacit Collusion in an Infinitely Repeated Prisoners' Dilemma

In the context of an infinitely repeated Prisoners' Dilemma, we explore how cooperation is initiated when players signal and coordinate through their actions. There are two types of players - patient and impatient - and a player's type is private information. An impatient type is incapable of cooperative play, while if both players are patient types - and this is common knowledge - then they can cooperate with a grim trigger strategy. We find that the longer that players have gone without cooperating, the lower is the probability that they'll cooperate in the next period. While the probability of cooperation emerging is always positive, there is a positive probability that cooperation never occurs.

Signaling and Tacit Collusion in an Infinitely Repeated Prisoners' Dilemma

In the context of an infinitely repeated Prisoners.Dilemma, we explore how cooperation is initiated when players signal and coordinate through their actions. There are two types of players - patient and impatient - and a player's type is private information. An impatient type is incapable of cooperative play, while if both players are patient types - and this is common knowledge - then they can cooperate with a grim trigger strategy. We find that the longer that players have gone without cooperating, the lower is the probability that they'll cooperate in the next period. While the probability of cooperation emerging is always positive, there is a positive probability that cooperation never occurs.

A study of helicopter stability and control including blade dynamics

A linearized model of rotorcraft dynamics has been developed through the use of symbolic automatic equation generating techniques. The dynamic model has been formulated in a unique way such that it can be used to analyze a variety of rotor/body coupling problems including a rotor mounted on a flexible shaft with a number of modes as well as free-flight stability and control characteristics. Direct comparison of the time response to longitudinal, lateral and directional control inputs at various trim conditions shows that the linear model yields good to very good correlation with flight test. In particular it is shown that a dynamic inflow model is essential to obtain good time response correlation, especially for the hover trim condition. It also is shown that the main rotor wake interaction with the tail rotor and fixed tail surfaces is a significant contributor to the response at translational flight trim conditions. A relatively simple model for the downwash and sidewash at the tail surfaces based on flat vortex wake theory is shown to produce good agreement. Then, the influence of rotor flap and lag dynamics on automatic control systems feedback gain limitations is investigated with the model. It is shown that the blade dynamics, especially lagging dynamics, can severly limit the useable values of the feedback gain for simple feedback control and that multivariable optimal control theory is a powerful tool to design high gain augmentation control system. The frequency-shaped optimal control design can offer much better flight dynamic characteristics and a stable margin for the feedback system without need to model the lagging dynamics

MAVS expressed by hematopoietic cells is critical for control of West Nile virus infection and pathogenesis

West Nile virus (WNV) is the most important cause of epidemic encephalitis in North America. Innate immune responses, which are critical for control of WNV infection, are initiated by signaling through pathogen recognition receptors, RIG-I and MDA5, and their downstream adaptor molecule, MAVS. Here, we show that a deficiency of MAVS in hematopoietic cells resulted in increased mortality and delayed WNV clearance from the brain. In Mavs(−/−) mice, a dysregulated immune response was detected, characterized by a massive influx of macrophages and virus-specific T cells into the infected brain. These T cells were polyfunctional and lysed peptide-pulsed target cells in vitro. However, virus-specific T cells in the brains of infected Mavs(−/−) mice exhibited lower functional avidity than those in wild-type animals, and even virus-specific memory T cells generated by prior immunization could not protect Mavs(−/−) mice from WNV-induced lethal disease. Concomitant with ineffective virus clearance, macrophage numbers were increased in the Mavs(−/−) brain, and both macrophages and microglia exhibited an activated phenotype. Microarray analyses of leukocytes in the infected Mavs(−/−) brain showed a preferential expression of genes associated with activation and inflammation. Together, these results demonstrate a critical role for MAVS in hematopoietic cells in augmenting the kinetics of WNV clearance and thereby preventing a dysregulated and pathogenic immune response. IMPORTANCE West Nile virus (WNV) is the most important cause of mosquito-transmitted encephalitis in the United States. The innate immune response is known to be critical for protection in infected mice. Here, we show that expression of MAVS, a key adaptor molecule in the RIG-I-like receptor RNA-sensing pathway, in hematopoietic cells is critical for protection from lethal WNV infection. In the absence of MAVS, there is a massive infiltration of myeloid cells and virus-specific T cells into the brain and overexuberant production of proinflammatory cytokines. These results demonstrate the important role that MAVS expression in hematopoietic cells has in regulating the inflammatory response in the WNV-infected brain

Data Management Systems (DMS): Complex data types study. Volume 1: Appendices A-B. Volume 2: Appendices C1-C5. Volume 3: Appendices D1-D3 and E

Two categories were chosen for study: the issue of using a preprocessor on Ada code of Application Programs which would interface with the Run-Time Object Data Base Standard Services (RODB STSV), the intent was to catch and correct any mis-registration errors of the program coder between the user declared Objects, their types, their addresses, and the corresponding RODB definitions; and RODB STSV Performance Issues and Identification of Problems with the planned methods for accessing Primitive Object Attributes, this included the study of an alternate storage scheme to the 'store objects by attribute' scheme in the current design of the RODB. The study resulted in essentially three separate documents, an interpretation of the system requirements, an assessment of the preliminary design, and a detailing of the components of a detailed design

Measurements of intrahost viral diversity require an unbiased diversity metric.

Viruses exist within hosts at large population sizes and are subject to high rates of mutation. As such, viral populations exhibit considerable sequence diversity. A variety of summary statistics have been developed which describe, in a single number, the extent of diversity in a viral population; such measurements allow the diversities of different populations to be compared, and the effect of evolutionary forces on a population to be assessed. Here we highlight statistical artefacts underlying some common measures of sequence diversity, whereby variation in the depth of genome sequencing may substantially affect the extent of diversity measured in a viral population, making comparisons of population diversity invalid. Specifically, naive estimation of sequence entropy provides a systematically biased metric, a lower read depth being expected to produce a lower estimate of diversity. The number of polymorphic loci per kilobase of genome is more unpredictably affected by read depth, giving potentially flawed results at lower sequencing depths. We show that the nucleotide diversity statistic π provides an unbiased estimate of diversity in the sense that the expected value of the statistic is equal to the correct value of the property being measured. Our results are of importance for studies interpreting genome sequence data; we describe how diversity may be assessed in viral populations in a fair and unbiased manner.Wellcom

The reform of Chinese state-owned ship crewing agencies and implications for China’s seafaring labour export

peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=tmpm2