Background noise spectra of global seismic stations

Over an extended period of time station noise spectra were collected from various sources for use in estimating the detection and location performance of global networks of seismic stations. As the database of noise spectra enlarged and duplicate entries became available, an effort was mounted to more carefully select station noise spectra while discarding others. This report discusses the methodology and criteria by which the noise spectra were selected. It also identifies and illustrates the station noise spectra which survived the selection process and which currently contribute to the modeling efforts. The resulting catalog of noise statistics not only benefits those who model network performance but also those who wish to select stations on the basis of their noise level as may occur in designing networks or in selecting seismological data for analysis on the basis of station noise level. In view of the various ways by which station noise were estimated by the different contributors, it is advisable that future efforts which predict network performance have available station noise data and spectral estimation methods which are compatible with the statistics underlying seismic noise. This appropriately requires (1) averaging noise over seasonal and/or diurnal cycles, (2) averaging noise over time intervals comparable to those employed by actual detectors, and (3) using logarithmic measures of the noise

Pre-existing virus-specific CD8+ T-cells provide protection against pneumovirus-induced disease in mice

Pneumoviruses such as pneumonia virus of mice (PVM), bovine respiratory syncytial virus (bRSV) or human (h)RSV are closely related pneumoviruses that cause severe respiratory disease in their respective hosts. It is well-known that T-cell responses are essential in pneumovirus clearance, but pneumovirus-specific T-cell responses also are important mediators of severe immunopathology. In this study we determined whether memory- or pre-existing, transferred virus-specific CD8 + T-cells provide protection against PVM-induced disease. We show that during infection with a sublethal dose of PVM, both natural killer (NK) cells and CD8 + T-cells expand relatively late. Induction of CD8 + T-cell memory against a single CD8 + T-cell epitope, by dendritic cell (DC)-peptide immunization, leads to partial protection against PVM challenge and prevents Th2 differentiation of PVM-induced CD4 T-cells. In addition, adoptively transferred PVM-specific CD8 + T-cells, covering the entire PVM-specific CD8 + T-cell repertoire, provide partial protection from PVM-induced disease. From these data we infer that antigen-specific memory CD8 + T-cells offer significant protection to PVM-induced disease. Thus, CD8 + T-cells, despite being a major cause of PVM-associated pathology during primary infection, may offer promising targets of a protective pneumovirus vaccine

New insights into the genetic etiology of Alzheimer's disease and related dementias.

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Network modeling and an evaluation of a CD proposed ISMS

This report briefly describes the improvements and corrections made to a seismic network performance modeling code called NetSim. After expanding its supporting database, the modified code was used to predict the detection and location performances of an International Seismic Monitoring System (ISMS) proposed early in 1995 by the Group of Scientific Experts (GSE) supporting the Comprehensive Test Ban Treaty (CTBT) negotiators. The performance estimates indicated that the primary network achieves or exceeds the GSE goal of detecting a fully coupled 1kiloton nuclear shot contained in consolidated rock anywhere on the earth. It was also shown that without calibrated regional location models, the primary network alone cannot achieve the GSE location accuracy requirement of 1000 square kilometers at the detection threshold of the primary network, but with the help of 67 auxiliary stations that goal can be achieved in the northern hemisphere. Once the regional location models become better calibrated, the predictions based on these models indicated that the primary network should be able to realize the GSE requirement throughout much of the world. However, the location accuracy requirement is not realized in Central America, on the oceanic islands, on continental margins in the southern hemisphere, and in Antarctica. The introduction of the 67 auxiliary stations into the calibrated network primarily broadens the regions already having good location accuracies. The location performance estimates may be regarded as conservative since the S-wave arrivals were not included A comprehensive set of scenarios are illustrated in this effort to better understand various influences on network performance

Robust and intelligent bearing estimation

As the monitoring thresholds of global and regional networks are lowered, bearing estimates become more important to the processes which associate (sparse) detections and which locate events. Current methods of estimating bearings from observations by 3-component stations and arrays lack both accuracy and precision. Methods are required which will develop all the precision inherently available in the arrival, determine the measurability of the arrival, provide better estimates of the bias induced by the medium, permit estimates at lower SNRs, and provide physical insight into the effects of the medium on the estimates. Initial efforts have focused on 3-component stations since the precision is poorest there. An intelligent estimation process for 3-component stations has been developed and explored. The method, called SEE for Search, Estimate, and Evaluation, adaptively exploits all the inherent information in the arrival at every step of the process to achieve optimal results. In particular, the approach uses a consistent and robust mathematical framework to define the optimal time-frequency windows on which to make estimates, to make the bearing estimates themselves, and to withdraw metrics helpful in choosing the best estimate(s) or admitting that the bearing is immeasurable. The approach is conceptually superior to current methods, particular those which rely on real values signals. The method has been evaluated to a considerable extent in a seismically active region and has demonstrated remarkable utility by providing not only the best estimates possible but also insight into the physical processes affecting the estimates. It has been shown, for example, that the best frequency at which to make an estimate seldom corresponds to the frequency having the best detection SNR and sometimes the best time interval is not at the onset of the signal. The method is capable of measuring bearing dispersion, thereby withdrawing the bearing bias as a function of frequency. The lowest measurable frequency in the dispersion pattern is often a near error free bearing. These latter features should be helpful in calibrating the stations for frequency dependent biases induced by the earth. Future efforts will enhance the SEE algorithm and will also evaluate it using larger station data sets

Performance estimates of the CD proposed international seismic monitoring system

An enhanced version of NetSim and an expanded supporting database were used to predict the detection and location performances of the International Seismic Monitoring System (ISMS) proposed in Working Paper 330 by the Ad Hoc Committee on a Nuclear Test Ban Treaty who supported the Conference on Disarmament in formulating the system monitoring requirements. The primary goals of this effort were to estimate the levels of 9 performance of the proposed ISMS and to predict the enhancements in location accuracy as would be provided by station and regional calibrations. An estimate of the detection threshold indicates that the primary network alone and in its mature state is capable of detecting a fully coupled 1 kiloton nuclear shot contained in consolidated rock anywhere on the earth. Further, the best detection thresholds appear in central Eurasia and range from 3.25 to 3.5 magnitude units. The threshold estimates were based on a 3P at 99% network detection criterion. Location performance estimates indicated that conventional location methods using regional and station calibrations are capable of achieving location accuracies better than 1000 square kilometers with 90% confidence largely everywhere for events with magnitudes at or above the detection threshold of the primary network. The poorest accuracies primarily appear on islands in the southern oceans and in portions of Antarctica. For events having a magnitude of 4.25 the location accuracy exceeds 100 square kilometers in almost the entire northern hemisphere, over a large portion of Africa, and a small portion of South America. Better accuracies than these are possible at larger event magnitudes. Regional and station calibrations yield net reductions in the elliptical areas of uncertainty by factors better than 6.0 using conventional location methods

Impact of sensor-scene interaction on the design of an IR security surveillance system

Recent encouraging developments in infrared staring arrays with CCD readouts and in real time image processors working on and off the focal plane have suggested that technologies suitable for infrared security surveillance may be available in a two-to-five year time frame. In anticipation of these emerging technologies, an investigation has been undertaken to establish the design potential of a passive IR perimeter security system incorporating both detection and verification capabilities. To establish the design potential, it is necessary to characterize the interactions between the scene ad the sensor. To this end, theoretical and experimental findings were employed to document (1) the emission properties of scenes to include an intruder, (2) the propagation and emission characteristics of the intervening atmosphere, and (3) the reception properties of the imaging sensor. The impact of these findings are summarized in the light of the application constraints. Optimal wavelengths, intruder and background emission characteristics, weather limitations, and basic sensor design considerations are treated. Although many system design features have been identified to this date, continued efforts are required to complete a detailed system design to include the identifying processing requirements. A program to accomplish these objectives is presented

The Feasibility of Monitoring Continuous Wave Sources with Seismic Arrays

This paper identifies and explores the technical requirements and issues associated with remotely monitoring continuous wave (CW) sources with seismic arrays. Potential approaches to this monitoring problem will be suggested and partially evaluated to expose the monitoring challenges which arise when realistic local geologies and cultural noise sources are considered. The selective directionality and the adaptive noise cancellation properties of arrays are required to observe weak signals while suppressing a colored background punctuated with an unknown distribution of point and sometimes distributive sources. The array is also required to characterize the emitters and propagation environment so as to properly focus on the CW sources of interest while suppressing the remaining emitters. The proper application of arrays requires an appreciation of the complexity of propagation in a non-homogeneous earth. The heterogeneity often limits the available spatial coherence and therefore the size of the army. This adversely impacts the array gain and the array's ability to carefully resolve various emitters. Arrays must also contend with multipath induced by the source and the heterogeneous earth. If the array is to focus on an emitter and realize an enhancement in the signal to noise ratio, methods must be sought to coherently add the desired signal components while suppressing interference which may be correlated with the desired signal. The impact of these and other issues on army design and processing are described and discussed