Probing Solar Convection

In the solar convection zone acoustic waves are scattered by turbulent sound speed fluctuations. In this paper the scattering of waves by convective cells is treated using Rytov's technique. Particular care is taken to include diffraction effects which are important especially for high-degree modes that are confined to the surface layers of the Sun. The scattering leads to damping of the waves and causes a phase shift. Damping manifests itself in the width of the spectral peak of p-mode eigenfrequencies. The contribution of scattering to the line widths is estimated and the sensitivity of the results on the assumed spectrum of the turbulence is studied. Finally the theoretical predictions are compared with recently measured line widths of high-degree modes.Comment: 26 pages, 7 figures, accepted by MNRA

Data base management system analysis and performance testing with respect to NASA requirements

Several candidate Data Base Management Systems (DBM's) that could support the NASA End-to-End Data System's Integrated Data Base Management System (IDBMS) Project, later rescoped and renamed the Packet Management System (PMS) were evaluated. The candidate DBMS systems which had to run on the Digital Equipment Corporation VAX 11/780 computer system were ORACLE, SEED and RIM. Oracle and RIM are both based on the relational data base model while SEED employs a CODASYL network approach. A single data base application which managed stratospheric temperature profiles was studied. The primary reasons for using this application were an insufficient volume of available PMS-like data, a mandate to use actual rather than simulated data, and the abundance of available temperature profile data

Solar-cycle variation of the sound-speed asphericity from GONG and MDI data 1995-2000

We study the variation of the frequency splitting coefficients describing the solar asphericity in both GONG and MDI data, and use these data to investigate temporal sound-speed variations as a function of both depth and latitude during the period from 1995-2000 and a little beyond. The temporal variations in even splitting coefficients are found to be correlated to the corresponding component of magnetic flux at the solar surface. We confirm that the sound-speed variations associated with the surface magnetic field are superficial. Temporally averaged results show a significant excess in sound speed around 0.92 solar radii and latitude of 60 degrees.Comment: To be published in MNRAS, accepted July 200

Determining solar abundances using helioseismology

The recent downward revision of solar photospheric abundances of Oxygen and other heavy elements has resulted in serious discrepancies between solar models and solar structure as determined through helioseismology. In this work we investigate the possibility of determining the solar heavy-element abundance without reference to spectroscopy by using helioseismic data. Using the dimensionless sound-speed derivative in the solar convection zone, we find that the heavy element abundance, Z, of 0.0172 +/- 0.002, which is closer to the older, higher value of the abundances.Comment: To appear in Ap

Asteroseismic Theory of Rapidly Oscillating Ap Stars

This paper reviews some of the important advances made over the last decade concerning theory of roAp stars.Comment: 9 pages, 5 figure

Technique of fuzzy tuned stochastic scanpaths for robot vision

The real-time processing of frame sequences obtained from cameras mounted on autonomous mobile robots and vehicles is a computationally intensive task. This paper is a review of the work carried out so far in the development of a procedure using fuzzy-tuned stochastic 'scanpaths' for efficiently scanning images in a frame sequence. A concise explanation of using fuzzy-tuned stochastic scanpaths is given here followed by a summary of the experimental work that has been undertaken to date and results achieved. The results show how the technique can reliably locate objects in scene whilst examining only a fraction of the image surface, e.g. 5%. The paper concludes with a discussion on research insofar accomplished and proposes ideas for future work

The effects of sodium bicarbonate supplementation at individual time-to-peak blood bicarbonate on 4-km cycling time trial performance in the heat.

The purpose of this study was to explore the effect of individualised sodium bicarbonate (NaHCO ) supplementation according to a pre-established individual time-to-peak (TTP) blood bicarbonate (HCO ) on 4-km cycling time trial (TT) performance in the heat. Eleven recreationally trained male cyclists (age: 28 ± 6 years, height: 180 ± 6 cm, body mass: 80.5 ± 8.4 kg) volunteered for this study in a randomised, crossover, triple-blind, placebo-controlled design. An initial visit was conducted to determine TTP HCO following 0.2 g.kg body mass (BM) NaHCO ingestion. Subsequently, on three separate occasions, participants completed a 4-km cycling TT in the heat (30 degrees centigrade; °C) (relative humidity ∼40%) following ingestion of either NaHCO (0.2 g.kg body mass), a sodium chloride placebo (0.2 g.kg BM; PLA) or no supplementation (control; CON) at the predetermined individual TTP HCO . Absolute peak [HCO ] prior to the 4-km cycling TT's was elevated for NaHCO compared to PLA (+2.8 mmol.l ;  = 0.002;  = 2.2) and CON (+2.5 mmol.l ;  < 0.001;  = 2.1). Completion time following NaHCO was 5.6 ± 3.2 s faster than PLA (1.6%; CI: 2.8, 8.3;  = 0.001;  = 0.2) and 4.7 ± 2.8 s faster than CON (1.3%; CI: 2.3, 7.1;  = 0.001;  = 0.2). These results demonstrate that NaHCO ingestion at a pre-established individual TTP HCO improves 4-km cycling TT performance in the heat, likely through enhancing buffering capacity

Causal Chain Analysis in Systematic Reviews of International Development Interventions

Understanding the extent to which an intervention ‘works’ can provide compelling evidence to decision-makers, although without an accompanying explanation of how an intervention works, this evidence can be difficult to apply in other settings, ultimately impeding its usefulness in making judicious and evidence-informed decisions. In this paper, we describe causal chain analysis as involving the development of a logic model, which outlines graphically a hypothesis of how an intervention leads to a change in an outcome. This logic model is then used to anchor subsequent decisions in the systematic review process, including decisions on synthesis. In this paper, we outline the steps taken in building a logic model, which usually consists of a series of boxes depicting intervention components and processes, outputs, and outcomes with arrows depicting connecting relationships. The nature of these connecting relationships and their basis in causality are considered, through a focus on complex causal relationships and the way in which contextual factors about the intervention setting or population may moderate these. We also explore the way in which specific combinations of intervention components may lead to successful interventions. Evidence synthesis techniques are discussed in the context of causal chain analysis, and their usefulness in exploring different parts of the causal chain or different types of relationship. The approaches outlined in this paper aim to assist systematic reviewers in producing findings that are useful to decision-makers and practitioners, and in turn, help to confirm existing theories or develop entirely new ways of understanding how interventions effect change

The variation of floods in the middle reaches of the Yangtze River and its teleconnection with El Niño events

International audienceMiddle reaches of the Yangtze River are the worst flooded segments along the Yangtze River. It is important to understand and study the variations of frequency and magnitude of historical floods in this area and how were they related to or affected by EI Niño in a long historical period. We applied the statistics and time series to study and analyze historical floods (1470-2000) and EI Niño events (1525-1995). The results show that the more floods occurred in the latest 200 years. The power-spectral analysis suggests the main cycle of flood variation is longer than that of EI Niño events. El Nino shows the fluctuations of about 2-year and 3~4 year period while the flood variation is not so significant but can also be identified in the period of 2, 8 and 40 years (it exceeds the level of confidence 0.03). Time series analyses of the fluctuation of flood and El Nino indicate that there is a significant correlation between the two at both high and moderate frequency sections. The result shows that the response of the floods along the middle reaches of the Yangtze River to the effects of El Nino events is not only delayed one or more than one year as suggested by many Chinese scientists, but it also can be somewhat longer delayed up to about 8 years. The result also indicates that the shorter the interval of EI Niño events, the sooner the flood events follows. In other words, flood could be delayed with longer time if the interval time of EI Niño events is longer