NOAA National Geodetic Survey

BACKGROUND: Many patients report symptomatic relief after undergoing arthroscopy of the knee for osteoarthritis, but it is unclear how the procedure achieves this result. We conducted a randomized, placebo-controlled trial to evaluate the efficacy of arthroscopy for osteoarthritis of the knee. METHODS: A total of 180 patients with osteoarthritis of the knee were randomly assigned to receive arthroscopic débridement, arthroscopic lavage, or placebo surgery. Patients in the placebo group received skin incisions and underwent a simulated débridement without insertion of the arthroscope. Patients and assessors of outcome were blinded to the treatment-group assignment. Outcomes were assessed at multiple points over a 24-month period with the use of five self-reported scores--three on scales for pain and two on scales for function--and one objective test of walking and stair climbing. A total of 165 patients completed the trial. RESULTS: At no point did either of the intervention groups report less pain or better function than the placebo group. For example, mean (+/-SD) scores on the Knee-Specific Pain Scale (range, 0 to 100, with higher scores indicating more severe pain) were similar in the placebo, lavage, and débridement groups: 48.9+/-21.9, 54.8+/-19.8, and 51.7+/-22.4, respectively, at one year (P=0.14 for the comparison between placebo and lavage; P=0.51 for the comparison between placebo and débridement) and 51.6+/-23.7, 53.7+/-23.7, and 51.4+/-23.2, respectively, at two years (P=0.64 and P=0.96, respectively). Furthermore, the 95 percent confidence intervals for the differences between the placebo group and the intervention groups exclude any clinically meaningful difference. CONCLUSIONS: In this controlled trial involving patients with osteoarthritis of the knee, the outcomes after arthroscopic lavage or arthroscopic débridement were no better than those after a placebo procedure.

A global Earth Magnetic Anomaly Grid (EMAG2) has been compiled from satellite, ship, and airborne magnetic measurements. EMAG2 is a significant update of our previous candidate grid for the World Digital Magnetic Anomaly Map. The resolution has been improved from 3 arc min to 2 arc min, and the altitude has been reduced from 5 km to 4 km above the geoid. Additional grid and track line data have been included, both over land and the oceans. Wherever available, the original shipborne and airborne data were used instead of precompiled oceanic magnetic grids. Interpolation between sparse track lines in the oceans was improved by directional gridding and extrapolation, based on an oceanic crustal age model. The longest wavelengths (>330 km) were replaced with the latest CHAMP satellite magnetic field model MF6. EMAG2 is available at http://geomag.org/models/EMAG2 and for permanent archive at http://earthref.org/cgi-bin/er.cgi?s=erda.cgi?n=970 .

The ecological importance of viruses is now widely recognized, yet our limited knowledge of viral sequence space and virus-host interactions precludes accurate prediction of their roles and impacts. In this study, we mined publicly available bacterial and archaeal genomic data sets to identify 12,498 high-confidence viral genomes linked to their microbial hosts. These data augment public data sets 10-fold, provide first viral sequences for 13 new bacterial phyla including ecologically abundant phyla, and help taxonomically identify 7-38% of 'unknown' sequence space in viromes. Genome- and network-based classification was largely consistent with accepted viral taxonomy and suggested that (i) 264 new viral genera were identified (doubling known genera) and (ii) cross-taxon genomic recombination is limited. Further analyses provided empirical data on extrachromosomal prophages and coinfection prevalences, as well as evaluation of in silico virus-host linkage predictions. Together these findings illustrate the value of mining viral signal from microbial genomes.

Measurements of soil moisture, both its global distribution and temporal variations, are required to study the water and carbon cycles. A global network of in situ soil moisture stations is needed to supplement datasets from satellite sensors. We demonstrate that signals routinely recorded by Global Positioning System (GPS) receivers for precise positioning applications can also be related to surface soil moisture variations. Over a three month interval, GPS‐derived estimates from a 300 m 2 area closely match soil moisture fluctuations in the top 5 cm of soil measured with conventional sensors, including the rate and amount of drying following six precipitation events. Thousands of GPS receivers that exist worldwide could be used to estimate soil moisture in near real‐time, with L‐band signals that complement future satellite missions.

This paper examines relationships between human resource management (HRM), work climate, and organizational performance in the branch network of a retail bank. It extends previous research on group‐level climate‐performance and HRM‐performance relationships and examines how climate and HRM function as joint antecedents of business unit performance. Significant correlations are found between work climate, human resource practices, and business performance. The results show that the correlations between climate and performance cannot be explained by their common dependence on HRM factors, and that the data are consistent with a mediation model in which the effects of HRM practices on business performance are partially mediated by work climate.

Surveys reflect societal change in a way that few other research tools do. Over the past two decades, three developments have transformed surveys. First, survey organizations have adopted new methods for selecting telephone samples; these new methods were made possible by the creation of large databases that include all listed telephone numbers in the United States. A second development has been the widespread decline in response rates for all types of surveys. In the face of this problem, survey researchers have developed new theories of nonresponse that build on the persuasion literature in social psychology. Finally, surveys have adopted many new methods of data collection; the new modes reflect technological developments in computing and the emergence of the Internet. Research has spawned several theories that examine how characteristics of the data collection method shape the answers obtained. Rapid change in survey methods is likely to continue in the coming years.

Motions of three hundred and sixty Global Positioning System (GPS) sites in Canada and the United States yield a detailed image of the vertical and horizontal velocity fields within the nominally stable interior of the North American plate. By far the strongest signal is the effect of glacial isostatic adjustment (GIA) due to ice mass unloading during deglaciation. Vertical velocities show present‐day uplift (∼10 mm/yr) near Hudson Bay, the site of thickest ice at the last glacial maximum. The uplift rates generally decrease with distance from Hudson Bay and change to subsidence (1–2 mm/yr) south of the Great Lakes. The “hinge line” separating uplift from subsidence is consistent with data from water level gauges along the Great Lakes, showing uplift along the northern shores and subsidence along the southern ones. Horizontal motions show outward motion from Hudson Bay with complex local variations especially in the far field. Although the vertical motions are generally consistent with the predictions of GIA models, the horizontal data illustrate the need and opportunity to improve the models via more accurate descriptions of the ice load and laterally variable mantle viscosity.

Measurements of soil moisture at various spatial and temporal scales are needed to study the water and carbon cycles. While satellite missions have been planned to measure soil moisture at global scales, these missions also need ground-based soil moisture data to validate their observations and retrieval algorithms. Here, we demonstrate that signals routinely recorded by Global Positioning System (GPS) receivers installed to measure crustal deformation for geophysical studies could be used to provide a global network of soil moisture sensors. The sensitivity to soil moisture is seen in reflected GPS signals, which are quantified by using the GPS signal to noise ratio data. We show that these data are sensitive to soil moisture variations for areas of 1000 m2 horizontally and 1-6 cm vertically. It is demonstrated that GPS signals penetrate deeper when the soil is dry than when it is wet. This change in penetration or ¿reflector¿ depth, along with the change in dielectric constant, causes the GPS signal strength to change its frequency and amplitude. Comparisons with conventional water content reflectometer sensors show good agreement (r <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> =0.9 to 0.76) with the variation in frequencies of the reflected GPS signals over a period of 7 months, with most of the disagreement occurring when soil moisture content is less than 0.1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Depression is a mental disorder characterized by persistent occurrences of lower mood states in the affected person. The electroencephalogram (EEG) signals are highly complex, nonlinear, and nonstationary in nature. The characteristics of the signal vary with the age and mental state of the subject. The signs of abnormality may be invisible to the naked eyes. Even when they are visible, deciphering the minute changes indicating abnormality is tedious and time consuming for the clinicians. This paper presents a novel method for automated EEG-based diagnosis of depression using nonlinear methods: fractal dimension, largest Lyapunov exponent, sample entropy, detrended fluctuation analysis, Hurst's exponent, higher order spectra, and recurrence quantification analysis. A novel Depression Diagnosis Index (DDI) is presented through judicious combination of the nonlinear features. The DDI calculated automatically based on the EEG recordings can be used to diagnose depression objectively using just one numeric value. Also, these features extracted from nonlinear methods are ranked using the t value and fed to the support vector machine (SVM) classifier. The SVM classifier yielded the highest classification performance with an average accuracy of about 98%, sensitivity of about 97%, and specificity of about 98.5%.

While deformation at the Earth's surface primarily occurs along tectonic plate boundaries, major earthquakes have shaken regions deep within continental interiors. Three of the largest (M &gt; 7.5) historic intraplate earthquakes occurred within the Indian subcontinent, suggesting the possibility of significant intraplate deformation. We consider surface velocities determined from new GPS data collected at 29 continuous GPS stations and 41 survey‐mode GPS stations in India between 1995 and 2007 to find a north‐south shortening rate of 0.3 ± 0.05 nanostrain yr −1 , which may be accommodated by 2 ± 1 mm/yr of more localized convergence across central India. Southward motions at 4–7 mm/yr of sites on the Shillong plateau in northeast India reflect rapid shortening and high earthquake hazard associated with active thrust faults bounding the plateau. The width and magnitude of the elastic strain accumulation field across the Himalaya varies little from ∼76°–90° longitude, but the strain is more broadly distributed and convergence rates are higher along the eastern ∼200 km of the range.

Abstract The North American gravity database as well as data-bases from Canada, Mexico, and the United States are being revised to improve their coverage, versatility, and accuracy. An important part of this effort is revising procedures for calculating gravity anomalies, taking into account our enhanced computational power, improved terrain databases and datums, and increased interest in more accurately defining long-wavelength anomaly components. Users of the databases may note minor differences between previous and revised database values as a result of these procedures. Generally, the differences do not impact the interpretation of local anomalies but do improve regional anomaly studies. The most striking revision is the use of the internationally accepted terrestrial ellipsoid for the height datum of gravity stations rather than the conventionally used geoid or sea level. Principal facts of gravity observations and anomalies based on both revised and previous procedures together with germane metadata will be available on an interactive Web-based data system as well as from national agencies and data centers. The use of the revised procedures is encouraged for gravity data reduction because of the widespread use of the global positioning system in gravity fieldwork and the need for increased accuracy and precision of anomalies and consistency with North American and national databases. Anomalies based on the revised standards should be preceded by the adjective “ellipsoidal” to differentiate anomalies calculated using heights with respect to the ellipsoid from those based on conventional elevations referenced to the geoid.

Reflected Global Positioning System (GPS) signals can be used to infer information about soil moisture in the vicinity of the GPS antenna. Interference of direct and reflected signals causes the composite signal, observed using signal-to-noise ratio (SNR) data, to undulate with time while the GPS satellite ascends or descends at relatively low elevation angles. The soil moisture change affects both the phase of the SNR modulation pattern and its magnitude. In order to more thoroughly understand the mechanism of how the soil moisture change leads to a change in the SNR modulation, we built an electrodynamic model of GPS direct and reflected signal interference, i.e., multipath, that has a bare-soil model as the input and the total GPS received power as the output. This model treats soil as a continuously stratified medium with a specific composition of material ingredients having complex dielectric permittivity according to well-known mixing models. The critical part of this electrodynamic model is a numerical algorithm that allows us to calculate polarization-dependent reflection coefficients of such media with various profiles of dielectric permittivity dictated by the soil type and moisture. In this paper, we demonstrate how this model can reproduce and explain the main features of experimental multipath modulation patterns such as changes in phase and amplitude. We also discuss the interplay between true penetration depth and effective reflector depth. Based on these modeling comparisons, we formulate recommendations to improve the performance of bare soil moisture retrievals from the data obtained using GPS multipath modulation.

Recapitulation An upward thrusting of masses of granitic rocks with accompanying slumping and partial upending of intermediary sedimentary and volcanic rocks has formed some of the ranges and intermontaine valleys of the Colorado River region westward from the mouth of the Grand Canyon. The Hemenway-Las Vegas-Callville Wash valley now occupied in part by the Callville basin of Lake Mead, a few miles north of Boulder Dam, is one of these intermontaine valleys, which has settled on faults separating this valley from the Black Mountains to the east and southeast, and on suspected faults which possibly are buried under detrital material along the southwest margin of the valley. These faults probably have been quiescent during Pleistocene and Recent times. However, we have strong evidence that this activity is being revived under the weight of the recently created Lake Mead. This lake has caused the underlying crustal blocks to be depressed probably several inches. In particular, the lower basin of the lake, which contains nearly one-third of the water load, has caused the block thereunder to undergo a downward movement along the above-mentioned faults, while the granitic masses on the opposite sides of the faults have remained relatively stationary. The semimountainous country several miles north of the lake probably is being affected in the downward movement. Evidence to support this belief is based in part on the following observations: Location of local earthquake epicenters has been possible by the employment of three seismological stations using temporary equipment and, later, small-model Benioff seismographs, placed in a triangular net about Lake Mead, and a fourth supplementary station at Boulder Dam. Seismological work is carried on by means of a coöperative program between the Bureau of Reclamation and the Coast and Geodetic Survey with the assistance of the National Park Service.

Abstract Amerasia Basin is the product of two phases of counterclockwise rotational opening about a pole in the lower Mackenzie Valley of NW Canada. Phase 1 opening brought ocean–continent transition crust (serpentinized peridotite?) to near the seafloor of the proto-Amerasia Basin, created detachment on the Eskimo Lakes Fault Zone of the Canadian Arctic margin and thinned the continental crust between the fault zone and the proto-Amerasia Basin to the west, beginning about 195 Ma and ending prior to perhaps about 160 Ma. The symmetry of the proto-Amerasia Basin was disrupted by clockwise rotation of the Chukchi Microcontinent into the basin from an original position along the Eurasia margin about a pole near 72°N, 165 W about 145.5–140 Ma. Phase 2 opening enlarged the proto-Amerasia Basin by intrusion of mid-ocean ridge basalt along its axis between about 131 and 127.5 Ma. Following intrusion of the Phase 2 crust an oceanic volcanic plateau, the Alpha–Mendeleev Ridge LIP (large igneous province), was extruded over the northern Amerasia Basin from about 127 to 89–75 Ma. Emplacement of the LIP halved the area of the Amerasia Basin, and the area lying south of the LIP became the Canada Basin.

GPS multipath, where a signal arrives by more than one path, is a source of positioning error which cannot be easily neutralized. Better understanding of the multipath environment, i.e., the direction of and distance to reflecting objects, is important for multipath mitigation during the site construction phase as well as discerning the impact of multipath on positioning estimates for existing sites. This paper presents a tool called power spectral mapping that visually represents the multipath environment of a GPS site. This technique uses the spectral content (frequency and magnitude) of signal‐to‐noise ratio (SNR) time series to determine which satellites, and therefore which portions of the antenna environment, contribute significant multipath error and at what frequencies. Wavelet analysis is used to extract the time‐varying frequency and magnitude content of various multipath constituents, and these data are projected onto a map representing the GPS antenna surroundings. Power spectral map examples from stations with very different multipath environments are presented. The maps are interpreted in terms of potential sources of multipath reflections, and how these multipath signals contribute to positioning error at each station is also assessed.

Global Positioning System vectors and surface tilt rates are inverted simultaneously for the rotation of western Oregon and plate locking on the southern Cascadia subduction thrust fault. Plate locking appears to be largely offshore, consistent with earlier studies, and is sufficient to allow occasional great earthquakes inferred from geology. Clockwise rotation of most of Oregon about a nearby pole is likely driven by collapse of the Basin and Range and results in shortening in NW Washington State. The rotation pole lies along the Olympic‐Wallowa lineament and explains the predominance of extension south of the pole and contraction north of it.

Abstract Some important oceanographic results have been obtained with Goddard Earth Models using satellite altimetry. GEM 9 and GEM 10 have been extended through the addition of worldwide GEOS‐3 altimetry to give new solutions, GEM 10B and IOC, fields that are complete in harmonics to degree 36 and 180, respectively. GEM 9 is a field derived solely from satellite tracking observations, whereas GEM 10 is a combination solution containing surface gravimetry. The accuracy of the oceanic geoid for these models has been estimated by using independent altimeter tracks of GEOS‐3. After empirically removing long wavelength orbital errors, residuals of 1.8 m (rms) were obtained for GEM 10, 0.94 m for GEM 10B, while GEM IOC gave 0.75 m. Large discrepancies, as much as 60 mgals, were found when ocean gravimetry anomalies (5° blocks) were compared to altimetry‐derived values. Altimeter values were verified through comparison with anomalies from GEM‐9, yielding an rms difference of only 5 mgals. An estimate of the long wavelength departures of the sea surface from the geoid has been made by comparing GEM‐9 to a geometrically derived altimetric surface. The value for the departure of the second degree zonal term was —43 ± 6 cm, an excess oblateness agreeing well with independent oceanographic data. SEASAT orbital accuracies will be of concern for the most effective use of its 10‐cm altimetry. We demonstrate with the use of crossover arcs of GEOS‐3 altimetry that significant errors in satellite gravitational perturbations have been removed by improving the geopotential field (in GEM 10B) with the GEOS‐3 altimeter and laser tracking data.

We review the development and status of GPS geodetic methods for high-precision global time and frequency comparisons. A comprehensive view is taken, including hardware effects in the transmitting satellites and tracking receiver stations, data analysis and interpretation, and comparisons with independent results. Other GPS techniques rely on single-frequency data and/or assume cancellation of most systematic errors using differences between simultaneous observations. By applying the full observation modelling of modern geodesy to dual-frequency observations of GPS carrier phase and pseudorange, the precision of timing comparisons can be improved from the level of several nanoseconds to near 100 ps. For an averaging interval of one day, we infer a limiting Allan deviation of about 1.4 × 10−15 for the GPS geodetic technique. The accuracy of time comparisons is set by the ability to calibrate the absolute instrumental delays through the GPS receiver and antenna chain, currently about 3 ns. Geodetic clock measurements are available for most of the major timing laboratories, as well as for many other tracking stations and the satellites, via the routine products of the International GPS Service.

The National Oceanic and Atmospheric Administration’s National Geodetic Survey (NGS) manages the National Continuously Operating Reference Station (CORS) system that comprises a network of over 1,350 sites, each containing a geodetic quality Global Navigation Satellite System receiver. This network is currently growing at a rate of about 15 sites per month. NGS collects, processes, and distributes data from these sites in support of high-accuracy three-dimensional positioning activities throughout the United States, its territories, and a few foreign countries. CORS data are also used by geophysicists, meteorologists, atmospheric and ionospheric scientists, and others in support of a wide variety of applications. This paper addresses the history of the CORS network, some of its applications, and plans for enhancing it within the next few years.

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