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More than 36 years have passed since the discovery of the infrared excess from circumstellar dust orbiting the white dwarf G29-38, which at 17.5 pc it is the nearest and brightest of its class. The precise morphology of the orbiting dust remains only marginally constrained by existing data, subject to model-dependent inferences, and thus fundamental questions of its dynamical origin and evolution persist. This study presents a means to constrain the geometric distribution of the emitting dust using stellar pulsations measured at optical wavelengths as a variable illumination source of the dust, which re-radiates primarily in the infrared. By combining optical photometry from the Whole Earth Telescope with 0.7-2.5 micron spectroscopy obtained with SpeX at NASA's Infrared Telescope Facility, we detect luminosity variations at all observed wavelengths, with variations at most wavelengths corresponding to the behavior of the pulsating stellar photosphere, but towards the longest wavelengths the light curves probe the corresponding time-variability of the circumstellar dust. In addition to developing methodology, we find pulsation amplitudes decrease with increasing wavelength for principal pulsation modes, yet increase beyond approximately 2 microns for nonlinear combination frequencies. We interpret these results as combination modes deriving from principal modes of identical l values and discuss the implications for the morphology of the warm dust. We also draw attention to some discrepancies between our findings and theoretical expectations for the results of the non-linearity imposed by the surface convection zone on mode--mode interactions and on the behavior of the first harmonic of the highest-amplitude pulsation mode., Comment: 12 pages, 6 figures, to be published in The Astrophysical Journal

We present a micro-mechanical terahertz (THz) detector fabricated on a silicon on insulator (SOI) substrate and operating at room-temperature. The device is based on a U-shaped cantilever of micrometric size, on top of which two aluminum half-wave dipole antennas are deposited. This produces an absorption extending over the $\sim 2-3.5$THz frequency range. Due to the different thermal expansion coefficients of silicon and aluminum, the absorbed radiation induces a deformation of the cantilever, which is read out optically using a $1.5\mu$m laser diode. By illuminating the detector with an amplitude modulated, 2.5 THz quantum cascade laser, we obtain, at room-temperature and atmospheric pressure, a responsivity of $\sim 1.5 \times 10^{8}$pm/W for the fundamental mechanical bending mode of the cantilever. This yields an noise-equivalent-power of 20 nW/Hz$^{1/2}$ at 2.5THz. Finally, the low mechanical quality factor of the mode grants a broad frequency response of approximately 150kHz bandwidth, with a response time of $\sim 2.5\mu$s.

Image classifiers based on convolutional neural networks are defined, and the rate of convergence of the misclassification risk of the estimates towards the optimal misclassification risk is analyzed. Under suitable assumptions on the smoothness and structure of the aposteriori probability a rate of convergence is shown which is independent of the dimension of the image. This proves that in image classification it is possible to circumvent the curse of dimensionality by convolutional neural networks.

Writing is often used as a tool for learning. However, empirical support for the benefits of writing-to-learn is mixed, likely because the literature conflates diverse activities (e.g., summaries, term papers) under the single umbrella of writing-to-learn. Following recent trends in the writing-to-learn literature, we focus on the underlying cognitive processes. We draw on the largely independent writing-to-learn and cognitive psychology learning literatures to identify important cognitive processes. The current experiment examines learning from three writing tasks (and one non-writing control), with an emphasis on whether or not the tasks engaged retrieval. Tasks that engaged retrieval (essay writing and free recall) led to better final test performance than those that did not (note-taking and highlighting). Individual differences in structure building (the ability to construct mental representations of narratives; Gernsbacher, 1990) modified this effect; skilled structure builders benefited more from essay writing and free recall than did less skilled structure builders. Further, more essay-like responses led to better performance, implicating the importance of additional cognitive processes such as reorganization and elaboration. Our results highlight how both task instructions and individual differences affect the cognitive processes involved when writing-to-learn, with consequences for the effectiveness of the learning strategy. [This paper was published in "Journal of Experimental Psychology: Applied" v23 n2 p115-127 Apr 2017.]

The Second Planck Catalogue of Compact Sources is a catalogue of sources detected in single-frequency maps from the full duration of the Planck mission and supersedes previous versions of the Planck compact source catalogues. It consists of compact sources, both Galactic and extragalactic, detected over the entire sky. Compact sources detected in the lower frequency channels are assigned to the PCCS2, while at higher frequencies they are assigned to one of two sub-catalogues, the PCCS2 or PCCS2E, depending on their location on the sky. The first of these catalogues covers most of the sky and allows the user to produce subsamples at higher reliabilities than the target 80% integral reliability of the catalogue. The PCCS2E contains sources detected in sky regions where the diffuse emission makes it difficult to quantify the reliability of the detections. Both the PCCS2 and PCCS2E include polarization measurements, in the form of polarized flux densities, or upper limits, and orientation angles for all seven polarization-sensitive Planck channels. The improved data-processing of the full-mission maps and their reduced noise levels allow us to increase the number of objects in the catalogue, improving its completeness for the target 80 % reliability as compared with the previous versions, the PCCS and ERCSC catalogues., Comment: 39 pages and 33 figures. This paper is one of a set associated with the 2015 data release from Planck. Version accepted by Astronomy and Astrophysics

The Planck mission detected thousands of extragalactic radio sources at frequencies from 28 to 857 GHz. Planck's calibration is absolute (in the sense that it is based on the satellite's annual motion around the Sun and the temperature of the cosmic microwave background), and its beams are well characterized at sub-percent levels. Thus Planck's flux density measurements of compact sources are absolute in the same sense. We have made coordinated VLA and ATCA observations of 65 strong, unresolved Planck sources in order to transfer Planck's calibration to ground-based instruments at 22, 28, and 43 GHz. The results are compared to microwave flux density scales currently based on planetary observations. Despite the scatter introduced by the variability of many of the sources, the flux density scales are determined to 1-2% accuracy. At 28 GHz, the flux density scale used by the VLA runs 3.6% +- 1.0% below Planck values; at 43 GHz, the discrepancy increases to 6.2% +- 1.4% for both ATCA and the VLA., Comment: 16 pages, 4 figures and 4 tables

We briefly review selected mathematical models that describe the dynamics of pattern formation phenomena in dip-coating and Langmuir-Blodgett transfer experiments, where solutions or suspensions are transferred onto a substrate producing patterned deposit layers with structure length from hundreds of nanometres to tens of micrometres. The models are presented with a focus on their gradient dynamics formulations that clearly shows how the dynamics is governed by particular free energy functionals and facilitates the comparison of the models. In particular, we include a discussion of models based on long-wave hydrodynamics as well as of more phenomenological models that focus on the pattern formation processes in such systems. The models and their relations are elucidated and examples of resulting patterns are discussed before we conclude with a discussion of implications of the gradient dynamics formulation and of some related open issues.

The European Space Agency's Planck satellite, dedicated to studying the early Universe and its subsequent evolution, was launched 14~May 2009 and scanned the microwave and submillimetre sky continuously between 12~August 2009 and 23~October 2013. In February~2015, ESA and the Planck Collaboration released the second set of cosmology products based on data from the entire Planck mission, including both temperature and polarization, along with a set of scientific and technical papers and a web-based explanatory supplement. This paper gives an overview of the main characteristics of the data and the data products in the release, as well as the associated cosmological and astrophysical science results and papers. The science products include maps of the cosmic microwave background (CMB), the thermal Sunyaev-Zeldovich effect, and diffuse foregrounds in temperature and polarization, catalogues of compact Galactic and extragalactic sources (including separate catalogues of Sunyaev-Zeldovich clusters and Galactic cold clumps), and extensive simulations of signals and noise used in assessing the performance of the analysis methods and assessment of uncertainties. The likelihood code used to assess cosmological models against the Planck data are described, as well as a CMB lensing likelihood. Scientific results include cosmological parameters deriving from CMB power spectra, gravitational lensing, and cluster counts, as well as constraints on inflation, non-Gaussianity, primordial magnetic fields, dark energy, and modified gravity., Comment: 40 pages, 24 figures

The Planck Catalogue of Compact Sources (PCCS) is the catalogue of sources detected in the first 15 months of Planck operations, the "nominal" mission. It consists of nine single-frequency catalogues of compact sources, both Galactic and extragalactic, detected over the entire sky. The PCCS covers the frequency range 30--857\,GHz with higher sensitivity (it is 90% complete at 180 mJy in the best channel) and better angular resolution (from ~33' to ~5') than previous all-sky surveys in this frequency band. By construction its reliability is >80% and more than 65% of the sources have been detected at least in two contiguous Planck channels. In this paper we present the construction and validation of the PCCS, its contents and its statistical characterization., Comment: 21 pages, 20 figures, submitted to A&A. This work is one of the papers associated with the 2013 release of data from the Planck mission

We report on analysis of 308.3 hrs of high speed photometry targeting the pulsating DA white dwarf EC14012-1446. The data were acquired with the Whole Earth Telescope (WET) during the 2008 international observing run XCOV26. The Fourier transform of the light curve contains 19 independent frequencies and numerous combination frequencies. The dominant peaks are 1633.907, 1887.404, and 2504.897 microHz. Our analysis of the combination amplitudes reveals that the parent frequencies are consistent with modes of spherical degree l=1. The combination amplitudes also provide m identifications for the largest amplitude parent frequencies. Our seismology analysis, which includes 2004--2007 archival data, confirms these identifications, provides constraints on additional frequencies, and finds an average period spacing of 41 s. Building on this foundation, we present nonlinear fits to high signal-to-noise light curves from the SOAR 4.1m, McDonald 2.1m, and KPNO 2m telescopes. The fits indicate a time-averaged convective response timescale of 99.4 +/- 17 s, a temperature exponent 85 +/- 6.2 and an inclination angle of 32.9 +/- 3.2 degrees. We present our current empirical map of the convective response timescale across the DA instability strip., Comment: Accepted for publication in the Astrophysical Journal

For many decades communities have been troubled by the criminal activities of youth gangs. This report looks at almost 30 years of information collected on gang problems in nearly 4,000 communities. The number of localities reporting gang problems increased between the 1970s and the 1990s, representing a tenfold increase in the number of cities and elevenfold increase in the number of counties reporting problems. By the late 1990s, all 50 states and the District of Columbia had reported gang problems and the problems were widely spread throughout small and large cities. The states with the largest number of problem cities were California, Illinois, Texas, Florida, and Ohio. The data provide support for the prediction that the rate of gang activity growth will decrease in the early 2000s, and some support for the prediction that the actual number of gang localities will decrease. Sections are included on the scope of gang growth over the decades; location of gang growth; trends in gang cities; and an update of selected data. Reasons for the increase in the number of gang-problems are attributed to many factors including drugs; immigration; gang names and alliances; migration; government policies; female-headed households; and gang subculture and the media. (Contains 5 appendixes, 37 tables, 22 figures and 55 references.) (Author/JDM)

There has been an increasing commitment to the notion of collaboration among professionals who have a responsibility for a client. However, the need for psychological services still seems to receive little impetus from teacher and principal requests. Furthermore, the teacher continues to operate as an isolated professional. Preservice education and the induction period for the teaching profession should be the primary emphasis for effecting the goal of making psychologists indispensable in the schools. Through planned collaborations in the field during preservice training, each professional could learn about the perspectives of the other along with an appreciation of potential professional collaborations. A second opportunity for reinforcing the earlier "bonding" experience of teachers and school psychologists is the critical need to provide new teachers with a supportive induction period as one means to address the attrition rate among teachers. The absence of a supportive network and work environment for teachers has been a long recognized handicap for this profession. The school psychology training program, through its faculty and/or students, along with local school psychological services staff can provide a valuable resource to such a program. Peer mediated learning strategies to promote teacher retention can also be facilitated by school psychologists through organization and promotion of collegial dialogue. (JBJ)

The present invention includes a method and apparatus for digital to analog conversion and reconstruction of multichannel electrocardiograms. The method may include receiving digital information representative of a plurality of independent signals, producing a plurality of analog outputs from said digital information wherein a first analog output is designated as a common reference, and imposing a predetermined voltage on a second analog output with respect to said common reference, which provides for a substantial recreation of the original independent signals. The apparatus may comprise a processor operable for receiving digital information representative of independent lead signals from a first ECG machine and digital to analog circuitry for substantially reproducing the original lead signals for analysis on a second ECG machine for convenient and efficient second opinions of cardiac data.

Professional school counselors operate under a myriad of working conditions, some more conducive to hosting interns than others. Potential site supervisors must have some framework from which to operate in order to provide optimum internship experiences. Guidelines are suggested that address expectations; training; mentoring; and communication that can serve as a catalyst for future proposals to assist the practitioners-site supervisor. (JDM)

Discusses why interventions directed toward victims of bullying are at risk of failure without fully understanding the cognitive, affective, and behavioral motives of the perpetrators of bullying and teasing incidents. Proposes that it is critical for school counselors to view the bully as involved in a symbiotic relationship with the victim. (Contains 54 references.) (GCP)

This report chronicles the East Hartford, Connecticut, Parents' Choice Project--an education voucher plan. The plan was intended to dovetail with the school system's already-existing open enrollment policy and was to include the area's private and parochial schools, as well as all the public schools. The feasibility and implementation studies investigated the community's attitudes toward a voucher plan, specified the kind of plan most appropriate for East Hartford, examined student transportation systems, and distributed information to parents about the plan. Even though the board of education finally failed to approve the project, the East Hartford school system was provided with improved budgeting, transportation, and student management systems as a result of the feasibility and implementation studies. Volume I of this document provides a general overview of the study, and Volume II presents the organizational and technical systems developed for the implementation of a voucher system. (Author/DS)

The University of Denver has developed an approach to residence hall living that is designed to significantly increase the positive effect of the environment on the student. Two residential programs complement the classroom environment by housing students with like or related academic interests and providing equipment related to the students' interests, thereby offering them the chance to manipulate and play, in an active manner, with the ideas that have been stimulated in the classroom. One program is designed for disciplines that predominantly use empirical methods, the other programs for disciplines dealing with symbolism and aesthetics. The academic performance of students living in the halls shows marked improvement, and resident retention within the halls, especially among students in the empirical hall, is four or five times the level achieved before the program began. (Author/MLF)

This report represents the findings of a study on violence by youth gangs in 12 major American cities, and deals with the following topics: (1) the rationale and methods for a national survey of youth gangs; (2) the existence and seriousness of the problem of youth gangs in 12 major American cities; (3) the size and scope of the youth gang problem; (4) the social characteristics of gang members in six cities; (5) gang-related killings and other officially-recorded crimes; (6) gang-member violence; (7) gang activities and the public schools; (8) past and future trends in youth gang crime; and (9) conclusions about urban gang violence in the 1970's. Also included are statistical tables and appendices as well as a separate summary report. The report concludes that (1) current youth gang violence is more lethal than in the past; (2) more citizens today are threatened by gang violence; and (3) violence and other illegal activities of youth gangs represent an extremely serious crime problem with little chance for decline. (HLM)

Addresses both the need to gather data related to pending federal legislation having an impact on the elementary school counselor, with the intent to provide the results of that data to members of Congress, and to heighten awareness of the need to provide elementary school counseling opportunities in the rural regions of one midwestern state. (KW)

The elementary school counselor plays a significant role in the aftermath of peer victimization in the school setting. Counselors increase their effectiveness when they are trained in crisis intervention, have worked in their schools to prevent such incidents from occurring, and have a plan to address victims' needs when bullying does occur. (LSR)

Examines a small rural public school's immediate and long-range postvention responses to a student suicide. Provides information from a psychological autopsy compiled in the months following the death. Discusses the implications of suicide postvention and the benefits of using a psychological autopsy approach as a postvention strategy. (RJM)

Although science and technology are interrelated fields of endeavor, they possess different knowledge bases and procedures. By teaching students how to solve both scientific and technological problems, secondary school educators can increase their literacy. In turn, students' confidence in dealing with the world will deepen, their individuality will be enhanced, and the meaning of citizenship will be sharpened. (MLH)

Explored African-American teachers' (n=24) preferences for and ratings of consultant effectiveness as a function of consultant race, consultant style, and teacher stage of racial identity development. Found no significant differences in preferences for either a same- or opposite-race consultant. Participants preferred and rated as more effective an instrumentally oriented consultant. (Author)

The purpose of this compendium is to provide tools for college and university counsel and administrators to consider their institution's approach concerning the balance of First Amendment values with the harm caused by racial harassment. Section I examines the development of the University of Michigan's initial policy broadly regulating harassment, offering background to the university's experience, the judge's decision, and the revised policy adopted in response to the court decision. Section II consists of sample policies adopted or proposed by colleges and universities, including Stanford University, University of Texas, University of California, University of Wisconsin, University of North Carolina at Charlotte, and Emory University. This section also includes the New York University School of Law's procedures for student discipline, including a broad definition of discipline for "bias," and the Harvard Law School Guidelines for student-sponsored speakers, which include a statement of principle on the "right to dissent" and some examples suggesting the limits of "acceptable dissent." Section III includes selected articles, commentary, and outlines, including, among others: "Public Response to Racist Speech: Considering the Victim's Story" (Mari J. Matsuda); "Looking Ahead to the 1990's: Constitutional Law and American Colleges and Universities" (Martha Minow); "Freedom of Expression under the First Amendment and Racial Harassment on Campus" (Jane Brandt Bulbin); "Racial Harassment at Universities: Legal Issues To Consider when Developing and Implementing a Racial Harassment Policy" (Walter B. Connolly, Jr., and Alison B. Marshall); "The Constitutional Status of Expressive Conduct after the Flag-Burning Decision" (Lawrence White); and "Bibliography: The First Amendment and Racial Harassment on Campus" (Jane Brandt Bulbin and others.) (JDD)

Astronauts experience sensorimotor disturbances after long-duration space flight. After a water landing, crewmembers may need to egress the vehicle within a few minutes for safety and operational reasons in various sea state conditions. Exposure to even low-frequency motions induced by sea conditions surrounding a vessel can cause significant motor control problems affecting critical functions. The first objective of this study was to document human visual performance during simulated wave motion below 2.0 Hz. We examined the changes in accuracy and reaction time when subjects performed a visual target acquisition task in which the location of the target was offset vertically during horizontal rotation at an oscillating frequency of 0.8 Hz. The main finding was that both accuracy and reaction time varied as a function of target location, with greater performance decrements occurring when vertical targets were acquired at perturbing frequencies of 0.8 Hz in the horizontal plane. A second objective was to develop a countermeasure, base d on stochastic resonance (SR), to enhance sensorimotor capabilities with the aim of facilitating rapid adaptation to gravitational transitions after long-duration space flight. SR is a mechanism by which noise can enhance the response of neural systems to relevant sensory signals. Recent studies have shown that applying imperceptible stochastic electrical stimulation to the vestibular system (SVS) significantly improved balance and oculomotor responses. This study examined the effectiveness of SVS on improving balance performance. Subjects performed a standard balance task while bipolar SVS was applied to the vestibular system using constant current stimulation through electrodes placed over the mastoid process. The main finding of this study was that balance performance with the application of SR showed significant improvement in the range of 10%-25%. Ultimately an SR-based countermeasure might be fielded either as preflight training to enhance adaptability, or as a miniature patch-type stimulator worn post flight.

Astronauts experience sensorimotor disturbances after long duration space flight. These crewmembers may need to egress the vehicle within a few minutes for safety and operational reasons in various sea state conditions following a water landing. Exposure to even low frequency motions induced by sea conditions surrounding a vessel can cause significant fine and gross motor control problems affecting critical functions. The objective of this study was to document human motor and visual performance during simulated wave motion in the 0.1 to 2.0 Hz range. We examined in 12 healthy subjects the changes in accuracy when performing a seated visual target acquisition task in which the location of target was offset vertically during horizontal full body rotation at an oscillating frequency of 0.8 Hz (peak velocity of 160 deg/s). The main finding was that the accuracy of performance degraded in 7 of 12 subjects when acquiring vertical targets at perturbing frequencies of 0.8 Hz in the horizontal plane by one step size. We also examined in a separate study on 12 healthy subjects seated dynamic visual acuity (DVA) task performance during vertical full body oscillations at perturbing frequencies of 2 Hz (peak to peak motion of 5 cm). The main finding was that DVA was significantly reduced when acquiring targets at perturbing oscillations at frequencies of 2 Hz in the vertical plane by approximately 1 chart line. Thus low frequencies of perturbations in the horizontal and vertical planes can cause decrement in visual performance.

At the request of the Exploration Systems Mission Directorate (ESMD) and the Constellation Program (CxP) Safety, Reliability; and Quality Assurance (SR&QA) Requirements Director, the NASA Engineering and Safety Center (NESC) participated in the Cx SR&QA Requirements forum. The Requirements Forum was held June 24-26; 2008, at GRC's Plum Brook Facility. The forums purpose was to gather all stakeholders into a focused meeting to help complete the process of refining the CxP to refine its Level II SR&QA requirements or defining project-specific requirements tailoring. Element prime contractors had raised specific questions about the wording and intent of many requirements in areas they felt were driving costs without adding commensurate value. NESC was asked to provide an independent and thorough review of requirements that contractors believed were driving Program costs, by active participation in the forum. This document contains information from the forum.

Several studies have shown that diminution of the high-frequency (HF; 150-250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease.

In situ measurements of atmospheric methane concentrations begun in the early 1980s show decadal trends, as well as large interannual variations, in growth rate. Recent research indicates that while wetlands can explain several of the large growth anomalies for individual years, the decadal trend may be the combined effect of increasing sinks, due to increases in tropospheric OH, and stabilizing sources. We discuss new 20-year histories of annual, global source strengths for all major methane sources, i.e., natural wetlands, rice cultivation, ruminant animals, landfills, fossil fuels, and biomass burning. We also present estimates of the temporal pattern of the sink required to reconcile these sources and atmospheric concentrations over this time period. Analysis of the individual emission sources, together with model-derived estimates of the OH sink strength, indicates that the growth rate of atmospheric methane observed over the last 20 years can only be explained by a combination of changes in source emissions and an increasing tropospheric sink. Direct validation of the global sources and the terrestrial sink is not straightforward, in part because some sources/sinks are relatively small and diffuse (e.g., landfills and soil consumption), as well as because the atmospheric record integrates multiple and substantial sources and tropospheric sinks in regions such as the tropics. We discuss ways to develop and test criteria for rejecting and/or accepting a suite of scenarios for the methane budget.

Measurements of atmospheric methane from a globally distributed network of air sampling sites indicate that the globally averaged CH4 growth rate increased from an average of 3.9 ppb/yr during 1995-1997 to 12.7 +/- 0.6 ppb in 1998. The global growth rate then decreased to 2.6 +/- 0.6 ppb during 1999, indicating that the large increase in 1998 was an anomaly and not a return to the larger growth rates observed during the late 1970s and early 1980s. The increased growth rate represents an anomalous increase in the imbalance between CH4 sources and sinks equal to approximately 24 Tg CH4 during 1998. Wetlands and boreal biomass burning are sources that may have contributed to the anomaly. During 1998, the globally averaged temperature anomaly was +0.67 C, the largest temperature anomaly in the modern record. A regression model based on temperature and precipitation anomalies was used to calculate emission anomalies of 11.6 Tg CH4 from wetlands north of 30 N and 13 Tg CH4 for tropical wetlands during 1998 compared to average emissions calculated for 1982-1993. In 1999, calculated wetland emission anomalies were negative for high northern latitudes and the tropics, contributing to the low growth rate observed in 1999. Also 1998 was a severe fire year in boreal regions where approximately 1.3x10(exp 5) sq km of forest and peat land burned releasing an estimated 5.7 Tg CH4

In situ measurements of atmospheric methane concentrations begun in the early 1980s show decadal trends, as well as large interannual variations, in growth rate. Recent research indicates that while wetlands can explain several of the large growth anomalies for individual years, the decadal trend may be the combined effect of increasing sinks, due to increases in tropospheric OH, and stabilizing sources. We discuss new 20-year histories of annual, global source strengths for all major methane sources, i.e., natural wetlands, rice cultivation, ruminant animals, landfills, fossil fuels, and biomass burning, and present estimates of the temporal pattern of the sink required to reconcile these sources and atmospheric concentrations over the time period. Analysis of the individual emission sources, together with model-derived estimates of the OH sink strength, indicates that the growth rate of atmospheric methane observed over the last 20 years can only be explained by a combination of changes in source emissions and an increasing tropospheric sink.

This report summarizes and updates the annual on-orbit performance between January I and December 31, 1994, for spacecraft built by or managed by the Goddard Space Flight Center (GSFC). During 1994, GSFC had 27 active orbiting satellites and I Shuttle-launched and retrieved 'free flyer.' There were 310 reported anomalies among 21 satellites and one GSFC instrument (TOMS). GOES-8 accounted for 66 anomalies, and SAMPES reported 155 'anomalies'. Of the 155 anomalies reported for all but SAMPEX, only 4 affected the spacecraft missions 'substantially' or greater, that is, presented a loss of more than 33% of the total missions. The most frequent subsystem anomalies were Instrument/Payload(44), Timing Command and Control(40), and Attitude Control Systems(33). Of the non-SAMPEX anomalies, 29% had no effect on the missions and 28% caused subsystem or instrument degradation and, for another 28%, no anomaly effect on the mission could be determined. Fifty-three percent of non-SAMPEX anomalies could not be classified according to 'type'; the other most common types were 'systemic'(35), 'random'(19), and 'normal or expected operation'(15). Forty percent of the anomalies were not classified according to failure category; the remaining most frequent occurrences were 'design problems'(50) and 'other known problems'(35).